The correct answer is B. Answer B is correct because only Technician B is correct. A beating noise occurs when two vibrating forces are adding to each other’s amplitude. However, two vibrating forces may also subtract from each other’s amplitude. The adding and subtracting of amplitudes in similar frequencies is called beating. The two forces are the tire and companion flange. In many cases, eliminating either of the disturbances can correct the condition. Technician A is incorrect because exhaust system movement noise is not RPM sensitive and occurs consistently. Answers A, C, and D incorrect because Technician B only is correct.

The correct answer is A. Answer A is correct because the owner or driver is the best resource to explain the nature of the noise. Answer B is incorrect because even though a scan tool may be needed during a diagnostic procedure, using a scan tool is not involved in the first step. Answer C is incorrect because reviewing vehicle specifications in the service information is not a first step in a diagnostic procedure though may be needed later to help find a root cause. Answer D is incorrect because while road testing a vehicle is important, interviewing the customer first to find the nature of the noise is the first step.

The correct answer is B. Answer B is correct because a cracked exhaust manifold will cause the two separated sections to vibrate and make a metallic sound similar to a faulty valve lifter. A quick test to check for an exhaust leak is to place a rag in the tailpipe and block off the exhaust flow. If the exhaust system is not leaking, pressure will build and force the rag out of the pipe. If there are leaks, hissing will be heard from the exhaust system through the leaks. An assistant may be needed to perform the test (to block off the tailpipe with a rag) while the Technician listens for exhaust leaks. While the test is being performed, a mechanic’s stethoscope may help pinpointing small leaks. Another testing option is to use a smoke machine with an exhaust pipe adapter and fill the exhaust system with smoke. With the engine off, any signs of smoke will pinpoint the location of the crack. Answer A is incorrect because a converter is located downstream from the engine and while an exhaust noise may be heard, the noise is unlikely to be caused by a cracked or leaking catalytic converter. Answer C is incorrect because a cracked intake manifold will cause a vacuum leak which may be heard as a hissing sound and is not likely to sound like a noisy valve lifer. Answer D is incorrect because the exhaust pipe is located downstream after the muffler and while an exhaust noise may be heard, the noise is unlikely to be caused by a cracked or leaking exhaust pipe.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because valve lifters and loose valve adjustments will create a top end tapping noise. Technician B is correct because an exhaust leak, especially at the exhaust manifold, may sound similar to noises made by lifters. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is B. Answer B is correct because an exhaust system back-pressure test is used to determine if there is a restriction that will create low power. One method to test for back-pressure is to use a vacuum gauge connected to the intake manifold vacuum and raise the engine rpm to 2000 rpm for two minutes. If the vacuum gauge falls as the engine is held at 2000 rpm, suspect a restricted exhaust system. The exhaust will begin to build-up at the restriction eventually backing up into the combustion chamber. The intake stroke will not be able to pull in as much air since the exhaust cannot fully escape. The backup will result in an engine that has low power or may even stall. Answer A is incorrect because vacuum will decrease if the exhaust is restricted when the engine speed is increased. Answer C is incorrect because vacuum will decrease if the exhaust is restricted when the engine speed is increased. Answer D is incorrect because vacuum will decrease if the exhaust is restricted when the engine speed is increased.

The correct answer is A. Answer A is correct because checking for exhaust backpressure by measuring engine vacuum is performed using intake manifold vacuum. Answers B, C, and D are incorrect because each are in the exhaust stream where a pressure gauge, not a vacuum gauge, is used to measure backpressure.

The correct answer is A. Answer A is correct because a water manometer compares very small amounts of pressure differential. The limits for acceptable backpressure in a majority of diesel engines is 3” of mercury or 14” of water column as measured with a water manometer. Conspicuous performance complaints are noticeable at approximately 30” to 40” of water. For this reason, diesel exhaust systems are design and require routine maintenance to minimize exhaust backpressure. Answer B is incorrect because a MAF sensor is used to help determine the amount of ERG that is needed. Answer C is incorrect because an A/C compressor speed sensor is used to detect if the drive belt is slipping or has broken. Answer D is incorrect because there are no sensors to measure the value on a diesel engine as there are on a gasoline engine such as the MAP sensor.

The correct answer is C. Answer C is correct because exhaust system backpressure can be measured directly by installing a pressure gauge into an exhaust opening. Exhaust backpressure restrictions can be measured through the oxygen sensor opening. Use a back pressure gauge and adapter or remove the inside of an old discarded oxygen sensor and thread in an adapter to convert to a pressure gauge. Answer A is incorrect because the spectrometer is used to measure the freezing point of coolant. Answer B is incorrect because a Magnehelic gauge or water manometer compares very small amounts of pressure differential. Answer D is incorrect because a vacuum gauge is used at the intake manifold to measure backpressure.

The correct answer is B. Answer B is correct because psi or pounds per square inch is the most common pressure unit in the English measuring system. Answer A is incorrect because inches of mercury can measure pressure though it is more commonly used to measure lack of pressure of vacuum. Answer C is incorrect because inches of water measure micro amounts of pressure and not high enough to measure boost pressure. Answer D is incorrect because inch pound is a torque measurement.

The correct answer is A. Answer A is correct because only Technician A is correct. Some mufflers are equipped with a small hole at the rear lower end to drain accumulated water. Water vapor will condense on the cooler portions of the exhaust system unless the engine is running long enough to fully warm the muffler above the boiling point which vaporizes the water. Technician B is incorrect because no maintenance is required and the any accumulated water will likely boil off. Answers C and D are incorrect because only Technician A is correct.

The correct answer is A. Answer A is correct because exhaust gas that escapes from an exhaust system, other than at the tailpipe, can enter the passenger area of a vehicle. Answers B, C, and D are incorrect because while each are a concern, each are not as significant as exhaust gases escaping potentially causing a dangerous or even fatal situation for the driver and/or passengers.

The correct answer is C. Answer C is correct because detonation is a symptom of an EGR valve that is always closed. Answers A, B, and D are incorrect because each are symptoms of an EGR valve that is always open.

The correct answer is B. Answer B is correct because on Exhaust Gas Recirculation (EGR) systems that use manifold vacuum, the EGR solenoid valve is commanded ON during part-throttle conditions and moderate load. Answer A is incorrect because an EGR valve is not opening during acceleration. Answer C is incorrect because the EGR valve is not opening during deceleration. Answer D is incorrect because the EGR valve is not opening at idle speed.

The correct answer is A. Answer A is correct because if the Exhaust Gas Recirculation (EGR) valve is stuck closed the combustion temperature will be high causing additional NOX gases. Answers B, C, and D are incorrect because each will cause excessive Hydrocarbons (HC) emissions and not excessive Oxides of Nitrogen (NOX) emissions.

The correct answer is D. Answer D is correct and the least likely symptom of low Exhaust Gas Recirculation (EGR) flow because stalling comes from an open EGR or too much flow that causes a lack of oxygen and a rough idle and stalling. Answer A is incorrect because high Oxides of Nitrogen (NOX) emissions are a symptom of low EGR flow. Answers B and C are incorrect because each is a symptom of low EGR flow.

The correct answer is D. Answer D is correct because the Vehicle Safety Certification (VSC) label is attached to the left side pillar post on the rearward-facing section of the left front door. The VSC label indicates the month and year of manufacture as well as the Gross Vehicle Weight Rating (GVWR), the Gross Axle Weight Rating (GAWR), and the Vehicle Identification Number (VIN). Answers A and B are incorrect because the VIN does not contain specific vehicle build information. Answer C is incorrect because the vehicle Emissions Control Information (VECI) label under the hood of the vehicle shows informative settings and emission hose routing information. The VECI label (sticker) can be located on the bottom side of hood, the radiator fan shroud, the radiator core support, or the strut towers.

The correct answer is C. Answer C is correct because the Vehicle Emissions Control Information (VECI) label typically includes engine identification, emissions standard that the vehicle meets, spark plug type and gap, and emission calibration codes. Answer A is incorrect because the Vehicle Identification Number (VIN) does not contain specific vehicle build information. Answer B is incorrect because a parts and accessories label only identifies the vehicle options and accessories. Answer D is incorrect because the Vehicle Safety Certification (VSC) label is attached to the left side pillar post on the rearward-facing section of the left front door and indicates the month and year of manufacture as well as the Gross Vehicle Weight Rating (GVWR), and the Gross Axle Weight Rating (GAWR).

The correct answer is C. The Vehicle Emissions Control Information (VECI) label is correct because the VECI label contains the emission certification, model year, spark plug type and gap and evaporative information. Answers A, B, and D are incorrect because each are not shown.

The correct answer is B. Answer B is correct because the 8th character of a Vehicle Identification Number (VIN) identifies which engine is used for that specific vehicle. The 2nd character identifies the vehicle manufacturer. The 3rd character identifies the vehicle type or division. The 4th and 5th character identify the carline or model. The 10th character identifies the vehicle build year. Answers A, C, and D are incorrect because each do not represent the eighth character of a VIN.

The correct answer is C. Answer C is correct because a Vehicle Safety Certification (VSC) label is shown in the above photo and the month and year of manufacture is directly listed. A VSC label is attached to the left side pillar post on the rearward-facing section of the left front door. A VSC label directly lists the manufacturer as well as the Gross Vehicle Weight Rating (GVWR), the Gross Axle Weight Rating (GAWR), and the Vehicle Identification Number (VIN). Answer A is incorrect because an emission calibration code is listed on a Vehicle Emissions Control Information (VECI) label located under the hood of a vehicle and lists informative settings and emissions information. Answer B is incorrect because country of manufacture information is part of a VIN. Answer D is incorrect because vehicle assembly plant information is not shown on a VSC label.

The correct answer is A. Answer A is correct because an exhaust system leak will cause a vehicle to have a high oxygen reading of 3.5% with normal Hydrocarbon (HC) and normal Carbon Monoxide (CO) readings. While oxygen readings alone are a good indicator of lean air/fuel mixtures, assure to compare the oxygen reading with the other exhaust gases. By comparing the readings, a Technician will be able to determine that there is not a lean air/fuel mixture problem and be able to diagnose a leaking exhaust that draws outside air into the exhaust stream. Answer B is incorrect because while a high oxygen reading is generally considered to be an indication of a lean air-fuel mixture, the other gases are normal which indicate that the oxygen levels are caused by something outside of the engine such as an exhaust leak. Answer C is incorrect because a rich mixture will cause both the HC and CO to be higher than normal. Answer D is incorrect because a defective spark plug will cause a higher level of unburned HC.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because to properly diagnose a faulty circuit, a Technician is to always perform voltage drop tests on the power side of all affected circuits. Technician B is correct because to properly diagnose a faulty circuit, a Technician is to always check voltage drops by performing voltage drop tests on the circuit grounds of all affected circuits. Technicians are to always use wiring diagrams when diagnosing electric/electronic circuits. Voltage drop tests are a dynamic resistance test. Answers A, B, and D are correct because both Technicians are correct.

The correct answer is A. Answer A is correct because Technicians are to never jump battery or power supply voltage to an exhaust system actuator while the exhaust system actuator is connected to a control circuit. Applying power to an actuator that is connected to a control circuit will potentially damage the control circuit. Many actuators operate on voltages supplied by the system computer and may operate at voltages other than battery voltage, typically about 5 volts. Answer B is incorrect because applying battery voltage to a battery or battery cable is safe due to the fact that both are at the same voltage level. Answer C is incorrect because connecting to a mechanical linkage will not cause harm except for a spark if battery voltage is applied. Answer D is incorrect because applying battery voltage to a driven component will not cause harm and instead is often used to check the operation of an actuator.

The correct answer is D. Answer D is correct and the exception because a defective Exhaust Gas Recirculation (EGR) valve itself cannot cause an EGR valve to melt. Answers A, B, and C are incorrect because each may cause the plastic sensors on an EGR valve to melt.

The correct answer is A. Answer A is correct because only Technician A is correct. A broken transmission mount will allow the engine to move up and down and cause portions of the exhaust system to hit the floor of the vehicle. Technician B is incorrect because a broken transmission mount would have no effect on exhaust system backpressure. Answers C and D are incorrect because only Technician A is correct.

The correct answer is D. Answer D is correct because both answers A and C are correct. The first check is to the mounting bolt holes and fasteners for damaged threads and repair if needed. Answer C is also correct because transmission fluid can soften the rubber used in the mount which may lead to a collapsed mount and or premature failure. Answer B is incorrect because removing mounts and placing opposing tension on two mounting plates is not necessary to thoroughly inspect a transmission mount.

The correct answer is A. Answer A is correct and the exception because a broken transmission mount will not cause a vehicle to jump out of gear. Answers B, C, and D are incorrect because each may result when a transmission mount breaks.

The correct answer is D. Answer D is correct and the exception because the majority of catalytic converters have universal bolt-on flanges that will adapt to most universal muffler systems. Answers A, B, and C are incorrect because each are commonly used when a universal muffler is installed.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because a six-point socket will prevent the fastener head from being rounded off especially if the fastener head is rusted and/or old. Technician B is also correct because using slip joint pliers will prevent damage to the remaining exhaust pipe. Answers A, B, and D are correct because both Technicians are correct.

The correct answer is D. Answer D is correct because pipe adapters are generally only needed for non-OEM exhaust components. Answers A, B, and C are incorrect because each are needed when a Technician uses an Original Equipment Manufacturer (OEM) exact fit replacement muffler.

The correct answer is B. Answer B is correct because a pipe adapter is shown in the above photo. A pipe adapter will allow for a connection to a catalytic converter or exhaust manifold. Answers A, C, and D are incorrect because each are not a pipe adapter and are not shown in the above photo.

The correct answer is A. Answer A is correct because the drain hole at the bottom of the muffler was clogged and condensation was unable to drain. Most mufflers have a small hole at the rear lower end to drain accumulated water. Water vapor will condense on the cooler portions of the exhaust system unless the engine is run long enough to fully heat the muffler above the boiling point and vaporize the water. Answers B, C, and D are incorrect because each will not cause rust to form on the bottom of a muffler.

The correct answer is A. Answer A is correct and the exception because routing is a part of the installation. Answers B, C, and D are incorrect because after an exhaust system instillation, the engine will need to be started and the exhaust system checked for leaks. After checking the exhaust system for leaks, a road test will need to be performed to check the vehicle for rattles and vibrations.

The correct answer is D. Answer D is correct because neither Technician A or Technician B is correct. Technician A is incorrect because a cat back exhaust system is a relatively simple power modification that will free up the exhaust gas flow and produce an engine note that is more pronounced than a stock muffler. The term cat back exhaust can be defined as the section of an exhaust system that attaches after the last catalytic converter in an exhaust system. Technician B is also incorrect because cracks in cast iron exhaust manifolds cannot be repaired using a gasket. Cracked cast iron exhaust manifolds require replacement. Stainless steel exhaust manifolds may be welded. Answers A, B, and C are incorrect because neither Technician is correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because a defective Air Fuel Ratio (AFR) sensor will cause excessive heat. Technician B is also correct because due to the shape of a substrate or brick, the substrate or brick can melt if the engine over fuels due to a misfire. The small oxidation section of a catalytic converter helps build heat for the reduction section that reduces the Oxides of Nitrogen (NOx) emissions in the rear brick on newer vehicles. Answers A, B, and D are correct because both Technicians are correct.

The correct answer is A. Answer A is correct because as the efficiency of a catalytic converter drops from deterioration, the switching rate of the rear O2 sensor signal will start to look like the front O2 sensor signal. When the rear O2 sensor signal reaches approximately 75% of the front O2 sensor signal, a Diagnostic Trouble Code (DTC) will be stored and the Malfunction Indicator Lamp (MIL) or “check engine light” will come on. Answer B is incorrect because a One-trip fault will cause the Malfunction Indicator Lamp (MIL) or “check engine light” to come on. Answer C is incorrect because the lack of efficiency in a catalytic converter will not cause a “limp in” operation mode. Answer D is incorrect because a catalytic converter fault will cause the Malfunction Indicator Lamp (MIL) or “check engine light” to come on though there will be no noticeable changes to engine operation.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because the tap test involves tapping on a catalytic converter with a rubber mallet. If the substrate inside the converter is broken, the converter will rattle. If the converter rattles, the brick is broken. Technician B is also correct because the catalytic converter monitor of an OBD II uses an upstream and downstream oxygen sensor to test catalyst efficiency. When the engine combusts a lean air–fuel mixture, higher amounts of oxygen flow through the exhaust into the converter. The catalyst materials absorb the oxygen for the oxidation process, thereby removing it from the exhaust stream. If a converter cannot absorb enough oxygen, oxidation does not occur. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because if tapping on the muffler with a rubber mallet and a noise is heard then the most likely cause is a broken internal baffle(s) inside the muffler. Technician B is also correct because the tap test for a catalytic converter is used to check the substrate. If the substrate or brick inside the converter is broken, the converter will rattle. If the converter rattles, the brick is broken. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is C. Answer C is correct because when working properly, the temperature of the outlet is at least 10% hotter than the temperature of the inlet. When a catalytic converter is not working, the inlet temperature is hotter than the outlet temperature. Answers A, B, and D are incorrect because when working properly, the outlet temperature is approximately 10% hotter than the inlet.

The correct answer is B. Answer B is correct because an exhaust manifold expands and contracts during the heating and cooling of an engine. Some areas of a heat shield are hotter than others and if a heat shield is missing, a manifold can warp and crack similar to the above photo. Answer A is incorrect because while a loose manifold may cause exhaust noise and warpage, a loose manifold will not likely cause the exhaust manifold to crack. Answer C is incorrect because while a failed manifold gasket may cause exhaust noise, a failed manifold gasket is not likely to cause the exhaust manifold to crack. Answer D is incorrect because while missing some manifold bolts may cause exhaust noise and warpage, the missing bolts are not likely to cause the exhaust manifold to crack.

The correct answer is D. Answer D is correct because neither Technician is correct. Technician A is incorrect because a cat back exhaust system is a relatively simple power modification that will free up the exhaust gas flow and produce an engine note that is more pronounced than a stock muffler. The term “cat back exhaust” can be defined as the section of an exhaust system that attaches after the last catalytic converter in an exhaust system. Technician B is incorrect because cracks in cast iron exhaust manifolds cannot be repaired using a gasket. Cracked manifolds exhausts need to be replaced. Stainless steel exhaust manifolds may be welded. Answers A, B, and C are incorrect because neither Technician is correct.

The correct answer is A. Answer A is correct because if an exhaust system is restricted or clogged, backpressure will build to the point that the exhaust manifold gasket will blow out. Answer B is incorrect because a defective Secondary Air Injection (SAI) pump would not cause an increase in exhaust restriction or backpressure. Answer C is incorrect because a missing heat shield will not cause an increase in exhaust restriction or backpressure. Answer D is incorrect because a stuck open Exhaust Gas Recirculation (EGR) valve will not cause an increase in exhaust restriction or backpressure.

The correct answer is B. Answer B is correct because the photo is of a cracked exhaust manifold. Answers A, C and D are incorrect because each are not a cracked manifold.

The correct answer is D. Answer D is correct and the exception because a resonator is not connected to a turbocharger. Answer A is incorrect because an air intake and an air filter are connected to a turbocharger. Answer B is incorrect because on some applications, an exhaust manifold is directly connected to the turbocharger. Answer C is incorrect because an oil feed line is connected to a turbo charger.

The correct answer is C. Answer C is correct because a catalytic converter is located at point C. Answer A is incorrect because a muffler is located at point A. Answer B is incorrect because a resonator is located at point B. Answer D is incorrect because the oxygen sensor is located at point D.

The correct answer is B. Answer B is correct because hangers are located at points B. Answer A is incorrect because an extension pipe is located at point C. Answer C is incorrect because a clamp is located at point D. Answer D is incorrect because a flange is located at point A.

The correct answer is C. Answer C is correct because an extension pipe is located at point C. Answers A is incorrect because hangers are located at points B. Answer B is incorrect because a clamp is located at point D. Answer D is incorrect because a flange is located at point A.

The correct answer is D. Answer D is correct because a clamp are located at point D. Answer A is incorrect because an extension pipe is located at point C. Answer B is incorrect because a flange is located at point A. Answer C is incorrect because hangers are located at points B.

The correct answer is D. Answer D is incorrect because neither Technician is the correct. Technician A is incorrect because the U-bolts on the clamps at the slip joints are required be positioned at a right angle to avoid contact with the ground. Technician B is incorrect because hangers are used to support the exhaust system and not to reduce the clearance between the exhaust system and the body. Answers A, B, and C, are incorrect because neither Technician is correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because the item in the photo is an engine mount from a transverse engine vehicle and will allow the exhaust system to contact the body causing a vibration. Technician B is correct because a broken or missing hanger will allow the exhaust system components to contact the underneath of the vehicle causing a vibration. Answers A, B, and D are correct because both Technicians are correct.

The correct answer is B. Technician B is correct because vacuum checks are used to test exhaust back pressure. If the exhaust system is restricted, pressure increases in the exhaust system. The increased pressure is called back pressure. Manifold vacuum will drop gradually if the engine is kept at a constant speed and the exhaust is restricted. The reason the vacuum will drop is that all exhaust leaving the engine at a higher engine speed cannot pass through the restriction. Technician A is incorrect because manifold vacuum is measured at a high idle (2000 to 2500 RPM). Answers C and D are incorrect because only Technician B is correct.

The correct answer is A. Answer A is correct because water is one of the primary sources of problems in Secondary Air Injection (SAI) systems. There are two typical causes of water contamination. The first cause is failure of the reed valve to seal due to breakage or loss of temper allowing water from the exhaust to enter the case. The second cause is that the reed valves can stick closed preventing air from getting to the catalyst. Answers B, C, and D are incorrect because each are not a primary source for a fault in a SAI system.

The correct answer is A. Answer A is correct because only Technician A is correct. An intercooler is most efficient when a turbocharger’s boost pressure is near maximum, typically above 15 psi or 100 kPa. The majority of intercoolers operate on an air-to-air principle, by feeding compressed air from the turbocharger through the intercooler and then into the intake manifold. The intercooler works like a radiator. Inside the intercooler, air passes through small tubes with thin fins attached. The heated compressed air flowing through the intercooler heats up the fins and the tubes and as the vehicle moves forward, the cool outside air flows across the fins pulling heat away from the tubes and fins. Heat transfer will occur constantly during engine operation. Technician B is incorrect because a stuck closed wastegate will raise boost pressure. On a mechanical wastegate, the spring pressure in the diaphragm controls the pressure at which the wastegate valve opens. The wastegate actuator is a spring-loaded pressure diaphragm that moves when air pushes against it. The air moves into the chamber of the wastegate actuator and presses on the diaphragm, overcoming spring force. The control linkage pushes the wastegate open allowing exhaust gases to bypass the turbine wheel which will reduce the boost pressure. The process will happen over again and as pressure drops, the wastegate closes and allows exhaust to flow to the turbine wheel again. The wastegate actuator receives pressure from a line connected to the intake manifold. Answers C and D are incorrect because only Technician A is correct.

The correct answer is B. Answer B is correct because a check valve is shown in the above photo. Answers A, C, and D are incorrect because each are components that are not shown in the above photo.

The correct answer is B. Answer B is correct because only Technician B is correct. A defective fuel pressure regulator may cause low fuel pressure resulting in reduced fueling on Bank 1. The condition will cause the AFRS 1/1 (air/fuel ratio sensor 1/1 circuit high voltage) to go high voltage setting Diagnostic Trouble Code (DTC) P0132. Short and long term fuel trim indicates an increase of 36% to a lean Air/Fuel ratio. The fuel pressure shown is only 30 psi. Technician A is incorrect because an intake manifold gasket leak (vacuum leak) will cause DTC P0131 AFRS 1/1 (air/fuel ratio sensor 1/1 circuit low voltage) at about 1.3 volts with a Lambda of 0.75 driving rich with low voltage. Answers C and D are correct because only Technician B is correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because when an engine is replaced, a new oxygen sensor will ensure that the replacement engine is operating within exhaust emission standards. Technician B is also correct because an oxygen sensor produces low voltage when an engine is running lean. A typical oxygen sensor is able to detect if exhaust is richer or leaner than 14.7:1. A two-step oxygen sensors compares the residual oxygen in the exhaust with the oxygen in the reference atmosphere (air inside the sensor) and indicates a rich or lean air fuel mixture of exhaust. Narrowband sensors work on a rich or lean principle. When the air fuel mixture is rich, the voltage output is around 0.8 to 0.9 volts and when the air fuel mixture is lean the voltage will drop to 0.3 volts or less. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is B. Answer B is correct because only Technician B is correct. A cracked exhaust manifold allows additional oxygen into the exhaust stream that affects oxygen sensor voltage. Technician A is incorrect because a clogged air filter raises hydrocarbon emissions and also affects oxygen and carbon monoxide levels. Answers A, C, and D are incorrect because only Technician B is correct.

The correct answer is C. Answer C is correct because catalytic converter flange kits are available for exhaust pipes of 2 1/4 inch Outside Diameter (OD) and are used for custom exhaust repairs as well as designed to work seamlessly with aftermarket replacement parts. Answers A, B, and D are incorrect because each will not repair a cracked flange.

The correct answer is B. Answer B is correct because only Technician B is correct. When a vehicle is OBDII compliant, a scan tool that can access mode 6 may be used to review the test results for each of the catalyst monitors. A lab scope may also be used to compare the upstream and downstream oxygen sensor patterns to determine if a catalytic converter is working efficiently. When using mode 6, research the specific codes that the manufacturer uses to identify each catalyst monitor as well as the coding for the actual results. Technician A is incorrect because catalytic converters that are damaged due to contamination, overheating, or age are to be tested to determine proper functioning. Manufacturer’s may not recommend a tap test and prefer checking a catalytic converter using a scan tool or infrared thermometer. A tap test is performed by tapping on a catalytic converter using a rubber mallet. If the substrate inside the converter is broken, the converter will rattle when struck with a mallet. If the converter rattles, a replacement converter is required. Answers A, C, and D are incorrect because only Technician B is correct.

The correct answer is C. Answer C is correct because the United States Environmental Protection Agency (USEPA) requires installers of aftermarket catalytic converters to retain the replaced converter for a period of 15 days. The requirement is enforced by the USEPA. Answers A, B, and D are incorrect because each are not the length of time that the USEPA require aftermarket installers to keep a catalytic converter after the converter has been removed from a vehicle.

The correct answer is C. Answer C is correct and the least likely because in 1986, the United States Environmental Protection Agency (EPA) issued new guidelines for the construction, efficiency and installation of aftermarket catalytic converters. EPA guidelines state that replacement converters are to be installed only in the following situations: 1. Vehicles manufactured prior to 1996 are to have more than 50,000 miles and a legitimate need for replacement that is documented. 2. In cases of OBD Il-equipped vehicles (1996 and later), the original equipment manufacturer’s 8-year/80,000-mile warranty is to be expired and a legitimate need for replacement is to be established and documented. 3. When a vehicle is missing a converter. 4. A state or local inspection program has determined that the existing converter needs replacement. Federal law prohibits removal or replacement of a properly functioning original equipment catalytic converter. Answers A, B, and D are incorrect because each are reasons for replacing catalytic converter.

The correct answer is D. Answer D is correct and the exception because a downstream oxygen sensor monitors converter operation and will not affect efficiency. Answers A, B and C are incorrect because each affect converter efficiency. A catalytic converter may fail for a number of common reasons including contamination, overheating, or physical damage. Contamination happens when the catalyst brick becomes coated by a substance such as lead, silicone from sealants, or carbon. The contaminant prevents the exhaust gases from interacting with the catalyst.

The correct answer is A. Answer A is correct and the least likely because a stable catalyst monitor signal is an indication of a properly functioning converter. If a monitor fluctuates from high to low, the converter is not working properly. Answers B, C, and D are incorrect because each indicate a failed converter.

The correct answer is A. Answer A is correct and the most likely because on the first trip a misfire condition can occur that may damage a Three-Way Catalyst (TWC) due to overheating. Specific on-board diagnostic items will cause the ECM to light-up or blink the Malfunction Indicator Lamp (MIL). The Diagnostic Trouble Code (DTC) and Freeze Frame data is then stored for later retrieval. The DTCs P0300 – P0306 are misfire (possible three-way catalyst damage) codes. Answers B, C, and D are incorrect because each are not the most likely to turn on a MIL.

The correct answer is D. Answer D is correct because Carbon Monoxide (CO) will increase when air flow is shut off to a Secondary Air Injection (SAI) System. A SAI system can be tested using a 5-gas exhaust gas analyzer. Start the engine and allow the engine to run until normal operating temperature is achieved. Connect the analyzer probe to the tailpipe and observe the exhaust readings for Hydrocarbons (HC) and Carbon Monoxide (CO). Using pinch-off pliers, shut off the air flow from the SAI system and observe the HC and CO readings. Answers A, B, and C are incorrect because each will not happen when air flow is shut off to a SAI system.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because when a check valve fails, hot exhaust can travel up and destroy the switching valve(s) and the air pump itself. When the engine is cold and before the oxygen sensor is hot enough to reach closed loop, the air flow is directed to the exhaust manifold(s) through a one-way check valve(s). The valves keep exhaust gases from entering the switching solenoids and the air pump itself. Technician B is correct because a check valve contains a spring-type metallic disc or reed that closes the air line under exhaust back pressure. Excessive back pressure can push the disc or reed open and exhaust gas will enter the switching valves and destroy the valves. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because Heated Oxygen Sensor (HO2S) voltages for both sensors are to remain under 350 mV because air is being directed to the exhaust ports. The Secondary Air Injection (SAI) pump is an electric type pump that requires no periodic maintenance. To check the operation of a SAI pump, the engine is to be at normal operating temperature in neutral at idle. Using a scan tool, enable the SAI pump system and watch the (HO2S) voltages for both bank 1 and bank 2 HO2S. If the HO2S voltages remain low during the test, the SAI pump, solenoid, and shut-off valve are operating satisfactorily. If the HO2S voltage does not remain low when the SAI pump is enabled, inspect the following: voltage at the SAI pump when energized, seized AIR pump, hoses, vacuum lines, pipes, all connections for leaks and proper routing, air flow going to the exhaust ports, SAI pump for proper mounting, or hoses and pipes for deterioration or holes. Answers B, C, and D are incorrect because each are the incorrect O2 voltages for both sensors to remain under when air is being directed to the exhaust ports.

The correct answer is C. Answer C is correct because loose, missing, or defective rubber hose is the exception. The Engine Control Module (ECM) controls diagnostics and a Diagnostic Trouble Code (DTC) was set. Answers A, B and D are incorrect because these will all cause DTC P1485 for AIR solenoid circuit fault.

The correct answer is B. Answer B is correct because during regeneration of the (diesel particulate filter) DPF is correct because high engine coolant temperature is a malfunction and it will set a DTC (diagnostic trouble code), turn on the check engine light and the EGR system will be disabled. Answers A, C and D are incorrect because they are not malfunctions that will set a DTC.

The correct answer is B. Answer B is correct because only Technician B is correct. Technicians are to always check for a restricted exhaust when replacing a failed EGR valve sensor. Technician A is incorrect because the lack of back pressure, is not caused by a partially clogged exhaust system and will not melt plastic sensors. Answers A, C, and D are correct because only Technician B is correct.

The correct answer is C. Answer C is incorrect and the exception because spark knock is a symptom of an Exhaust Gas Recirculation (EGR) valve that is always closed. Answers A, B, and D are incorrect because each are likely symptoms of an EGR valve that is always open.

The correct answer is B. Answer B is correct because when circuit 39 is open the voltage is zero and the Engine Control Module (ECM) computes that the Exhaust Gas Recirculation (EGR) valve is closed by position, so then the ECM opens the valve. Answer A is incorrect because a defective ECM will not be able to set diagnostic codes. Answers C and D are incorrect because their failure will result in no EGR valve operation.

The correct answer is A. Answer A is correct because on systems that use manifold vacuum, the Exhaust Gas Recirculation (EGR) solenoid valve is commanded ON during part-throttle conditions and moderate load. The emission rules are for part-throttle operation. Answers B, C and D are incorrect because vacuum operated EGR valves do not function during acceleration, deceleration, or at idle.

The correct answer is C. Answer C is correct because the fill tube location for Diesel Exhaust Fuel (DEF) is often located near the diesel fuel fill tube. Answers A, B, and D are incorrect because each are not a location for DEF to be added.

The correct answer is A. Answer A is correct because only Technician A is correct. A two-wire oxygen sensor has a signal wire and a ground wire. A 3-wire oxygen sensor design uses an electric resistance heater to quickly raise the temperature and to help keep the sensor at operating temperature even at idle speeds. The three wires include a signal wire, a power wire, and a ground wire for the heater. A 4-wire oxygen sensor is a heated sensor that uses a signal wire and signal ground. The other two wires are the power and ground wires for the heater. Technician B is incorrect because a sensor produces a low voltage when running lean. An oxygen sensor is able to detect if an exhaust is richer or leaner than 14.7:1. A voltage reading of 900 mV will be rich and a reading of 300 mV will be lean. Answers C and D are correct because only Technician A is correct.

The correct answer is B. Answer B is correct because a lean air–fuel mixture causes misfire resulting in high Hydrocarbon (HC) emissions. When the propane was introduced into the intake stream the Heated Oxygen Sensor (HO2S) responded showing the system was working and not a problem with the sensor or ECM as well as there were no Diagnostic Trouble Codes (DTCs) present. A HO2S output voltage of 100 to 300 mV indicates the system is operating lean. The PCM determines base injector pulse width based on readings from the sensors & calculations from lookup tables stored in Read-Only Memory (ROM). Fuel trim uses oxygen sensor data to fine tune the air fuel mixture to ensure lowest emissions. Lean air-fuel mixture can be caused by low fuel pump pressure, a clogged fuel filter, or a restricted fuel injector. Answers A, C, and D are incorrect because each are not the most likely cause for the action and reaction of the O2 voltage.

The correct answer is A. Answer A is correct because when a replacement catalytic converter is installed, it is common practice to use slip joint fittings that are secured with clamps. Answers B, C, and D are incorrect because each strongly indicates strong evidence of emission system tampering.

The correct answer is D. Answer D is correct because a high idle is not necessarily a cause or indication of an emission test failure. Answers A, B, and C are incorrect because each will cause a vehicle to fail an emission inspection and are evidence of tampering.

The correct answer is B. Answer B is correct because tampering is the process of removing, disconnecting, altering, bypassing, or rendering ineffective any pollution control equipment installed in a motor vehicle. Tampering with a vehicle’s emissions control system is illegal and can negatively affect vehicle performance, void warranties, and contribute to air pollution. Answers A, C, and D are incorrect because each are not the term used to describe the removing, disconnecting, altering, and bypassing of any pollution control equipment.

The correct answer is D. Answer D is incorrect because neither Technician is correct. Technician A is incorrect because installing a flex pipe as a replacement for a catalytic converter is not legal and is considered to be tampering. Technician B is also incorrect because installing a converter test pipe to reduce backpressure is not legal and is considered to be tampering. Answers A, B, and C are incorrect because both Technicians are incorrect.

The correct answer is B. Answer B is correct because failing a state emissions test is a strong indication of catalytic converter failure. Answer A is incorrect because when a catalytic converter is failing typically there will be a decrease in engine performance. Answer C is incorrect because typically gas milage decreases when there is a catalytic converter failure. Answer D is incorrect because a clogged catalytic converter will restrict exhaust gases allowing the exhaust to accumulate creating dark smoke from the tailpipe.

The correct answer is A. Technician A is correct because a program card may be used on a three year old vehicle. The majority of program card makers supply cards for all vehicles except for a few older vehicles, specialty vehicles, and low production vehicles. Technician B is incorrect because custom bending is not necessary when a program card is available. Answers C and D are correct because only Technician A is correct.

The correct answer is D. Answer D is correct because a flex pipe allows for engine movement. There is considerable up twisting action on a transverse mounted 4-cylinder engine in a front wheel drive vehicle. Answers A, B, and C are incorrect because each are not a reason to install a flex pipe on a Front Wheel Drive Vehicle (FWD).

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because when fabricating an exhaust system, before bending, always consult the service information to review the system configuration. Technician B is also correct because a BendData card system guides a Technician step-by-step when fabricating original equipment exhaust and tailpipes. Answers A, B, and C are incorrect because both Technicians are incorrect.

The correct answer is C. Answer C is correct because an exhaust system build program card is shown in the above illustration. Answers A, B, and D are incorrect because the above photo is of a program card.

The correct answer is A. Answer A is correct and the exception because pre-manufacturing is not a method for pipe bending. Answers B, C, and D are incorrect because each are methods used to bend pipes.

The correct answer is C. Answer C is correct because custom bending is necessary when there is no program card or existing pipe. Custom bending may also be necessary when installing other than the original exhaust. Answer A is incorrect because pattern bending requires the original pipe to create the pattern. Answers B and D are incorrect because each are not used when there is not a program card or existing pipe.

The correct answer is B. Answer B is correct because only Technician B is correct. All program card bending information is to be thoroughly read and understood before proceeding with a bending operation. Technician A is incorrect because to properly bend a pipe, the make, model, year, and engine information that is provided on a program card will be needed. Answers C and D are incorrect because only Technician B is correct.

The correct answer is B. Answer B is correct because when bending an exhaust pipe using a program card the pipe is to be marked with a permanent marker where the bends will be made. The last mark represents the final cutoff point. Answers A, C, and D are incorrect because each are not the last mark made on an exhaust pipe.

The correct answer is A. Answer A is correct because a program card lists the length and diameter of a pipe, the distance between the center of the bends, and the rotation and depth of the bends in degrees. There may also be remarks that describe bending instructions for irregular applications. Answers B, C, and D are incorrect because each are linear measurements and are not used to measure the rotation and depth of bends.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because for the best performance, keeping exhaust system length as well as bends and elbows to a minimum will keep backpressure low. Technician B is also correct because the longer the exhaust system becomes and the greater the number or sharpness of bends, the slower the exhaust gases will flow. Resistance to exhaust gas flow will also increases backpressure. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because stretching and compressing flex pipe during initial installation will limit the tubing’s ability to absorb engine vibration and thermal expansion and will reduce the life span of the pipe. Answer B is incorrect because flex pipes are to be used on FWD vehicles. Answer C is incorrect because flex pipe help reduce exhaust noise. A well-supported exhaust system will reduce the noise generated by vibration of exhaust pipes and the muffler shell. Answer D is incorrect because flex pipe itself will not improve gas flow.

The correct answer is A. Answer A is correct because when a flange is used to secure a pipe, such as an exhaust pipe to an exhaust manifold, assure that the flange is installed before the end of the pipe is flared. Answers B, C, and D are incorrect because each are not a needed action.

The correct answer is B. Answer B is correct because only Technician B is correct. If both pipes are the same diameter, the end of one pipe is to be enlarged to fit over the other pipe. Technician A is incorrect because common type is a slip-joint connection where an inner pipe fits inside an outer pipe. Answers C and D are incorrect because only Technician B is correct.

The correct answer is A. Answer A is correct because the maximum temperature in an automobile exhaust system is around 1,322 to 1,562 degrees Fahrenheit. The selected material for manufacturing an exhaust system will be able to deal with temperatures in the range of 1,322 to 1,562 degrees Fahrenheit. Answers B, C, and D are incorrect because each are not an approximate maximum temperature range that an exhaust system is able operate.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because if the tube material is too thin relative to the diameter, the tube will collapse as the outside of the tube wall elongates and thins during bending. Technician B is also correct because the tighter the bend radius, the smaller the degree of bend is possible and that more material is required to elongate. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because the use of good quality material is the first step in preventing collapse. Technician B is also correct because by adhering to standard material thickness specifications, which are often embossed on the tubing, pipe collapses can be prevented. Answers A, B, and D are correct because both Technicians are correct.

The correct answer is A. Answer A is correct because a neutral flame is a general heating flame and will typically have no chemical effect on the metal being welded. A neutral flame will not oxidize the weld metal and will also not cause an increase in the carbon content of the weld metal. For most welding operations the neutral flame is correct though other types of flames are occasionally needed for special welds. Non-ferrous alloys and high carbon steels may require a reducing flame while zinc bearing alloys may require an oxidizing flame. Answer B is incorrect because an oxidizing flame occurs when the ratio of oxygen to acetylene is changed to give an excess of oxygen. An oxidizing flame is observed when welders add more oxygen to a neutral flame. An oxidizing flame is useful for welding copper base alloys, zinc base alloys, cast iron, and manganese steel. Answer C is incorrect because in the welding zone, a carburizing flame provides a strong reducing atmosphere. A carburizing flame is useful for materials which are readily oxidized like oxygen free copper alloys. A carburizing flame is also used for high carbon steels, cast iron, and hard surfacing with high speed steel and cement carbides. A reducing flame has an approximate temperature of 5500°F which is lowest among all of the three flames. Answer D is incorrect because there is no soldering flame.

The correct answer is A. Answer A is correct because a neutral flame consists of a sharp cone extended from the tip of torch and is surrounded by an envelope. A neutral flame is obtained when approximately one volume of oxygen and one volume of acetylene are mixed. The term “neutral” is used because a neutral flame will typically have no chemical effect on the metal being welded. A neutral flame will not oxidize the weld metal and will also not cause an increase in the carbon content of the weld metal. Neutral gas welding flames may be used to weld mild steel, stainless steel, aluminum, cast iron, and copper. Answers B, C, and D are incorrect because each are not tasks for the use of a neutral flame.

The correct answer is A. Answer A is correct because c-clamps will help hold tubing together before beginning a weld. Assure to fit all the tubing in a preferred configuration as adjustments need to be accounted for when using c-clamps. Answer C is incorrect because before welding, clamping pipes and components in place is the best practice. Answers B and D are incorrect because each are actions that are not to be performed.

The correct answer is B. B is the correct answer because consulting a heat chart for the particular joint and gauge of metal is necessary to prevent damage during the welding process. Answers A, C, and D are incorrect because even though they are important steps, they should not be the first step.

The correct answer is A. Technician A only is correct because the further the gun is held from the work, the further the wire must extend to make contact with the metal being welded. Technician B is incorrect because the length of the wire between the gun and the base metal is called the stickout and has a significant effect on the quality of the weld. Normal stickout is usually around 3/8 inch. Allowing the tip of the gun to creep further away from the metal increases the stickout and puts less heat into the metal and can decrease the coverage of the gas shield. Answers C and D are incorrect because only Technician A is correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because for 90-degree angle fillet welds, the gun is normally held at a 45-degree angle which the angle may need to be modified for thinner metals. Technician B is also correct because If a fillet weld is configured as an inverted T the horizontal portion can dissipate heat on both sides of the weld. The vertical element ends at the weld, so it cannot dissipate as much heat and may causes burn-through. Angling the gun slightly away from the vertical element will help reduce burn-through. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because it is easier and better to tack weld exhaust components using a Metal Inert Gas (MIG) welder. Technician B is also correct because an oxyacetylene welder can be used to cut, heat, and weld metal. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because checking gun movement is the least likely procedure listed. Gun movement is determined during the actual welding operation. Moving the gun too slow will likely burn through the metal. Moving the gun too fast will likely result in welds that do not penetrate the metal surface. Answers B, C, and D are incorrect because they are all part of MIG setup.

The correct answer is D. Answer D is correct and the exception because using several electrodes will increase the cost of the repair. Another disadvantage of stick welding is that it can lead to the production of slag which can lead to leaks in the exhaust. Answers A, B, and C are incorrect because they are all part of using stick welding to make an exhaust system repair.

The correct answer is B. Answer B is correct because a harsh, high velocity flame will occur and will blow the molten metal from the puddle. Oxygen is added into the flame by opening the oxygen valve on the torch. Adjusting the two valves (cutting torch oxygen and acetylene) until a short, bright blue flame appears at the torch tip with no yellow color. An oxidizing action can be obtained by increasing the oxygen flow while a reducing action will result from increasing the acetylene flow. Both adjustments are valuable aids in welding. The actual adjustment of the flame depends on the type of material to be joined. Answers A, C, and D are incorrect because these will not occur.

The correct answer is A. Answer A is correct because technician A only is correct because the torch tip should be positioned above the metal plate so that the white cone is at a distance of 1.5 to 3.0mm from the plate. Technician B is incorrect because the torch should be held at a 45 to 60-degree angle from the horizontal plane. Answers C and D are incorrect because only Technician A is correct.

The correct answer is A. Answer A is correct because raising the acetylene pressure to 20 psi is LEAST LIKLEY required for oxyacetylene torch cutting. After heating the metal until it is cherry red, a jet of pure oxygen is needed that burns and oxidizes the metal during the cutting operation. Answers B, C, and D are incorrect because these tasks are required.

The correct answer is A. Answer A is correct because Technician A only is correct. An acetylene cylinder is protected by number of fusible plugs, which will melt at 220°F (104°C). If the cylinder is exposed to excessive heat, the plugs will melt and release the gas. Small cylinders (10 cu-ft. and 40 cu-ft. sizes) include one fusible metal channel located in the cylinder valve. Technician B is incorrect because transporting cylinders without the safety caps in place can be extremely dangerous. Fuel and oxygen tanks should be fastened securely upright to a post or a portable cart. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because increasing the speed of welding travel will add more filler rod to the molten puddle. The welder must also keep the filler metal in the hot outer flame zone when not adding it to the puddle to protect filler metal from oxidation. The Technician should not let the welding flame burn off the filler metal. The metal will not wet into the base metal and will appear to be a series of cold dots on the base metal. A cold weld offers very little strength. When the filler metal is properly added to the molten puddle, the resulting weld will be stronger than the original base metal. Answers B, C, and D are incorrect because each procedure should not be done if the welding bead gets too wide.

The correct answer is A. Answer A is correct because the weld area will not be as hot. The additional distance will reduce the heat at the welding puddle. Answers B, C, and D are incorrect because they will not occur if the distance increases between the tip of the gun and the metal being welded.

The correct answer is B. Answer B is correct because blue is. Answer A is incorrect because the Acetylene hose is red. Answer C is incorrect because the oxygen tank is green. Answer D is incorrect because yellow is not used.

The correct answer is B. Answer B is correct because the welding head is replaced with a cutting attachment. The main difference between the cutting torch and the welding torch is the cutting torch has an additional tube for high-pressure oxygen, along with a cutting tip or nozzle. Answers A, C, and D are incorrect because they are not substituted when the oxyacetylene torch is used for cutting.

The correct answer is D. Answer D is correct and the exception because keeping a bucket of water nearby will serve no purpose and offer no protection in the event of a fire. Water is not sufficient to put out this type of fire. The plasma cutting arc blows out hot metal and sparks, especially during the initial piercing of the metal. It also heats the workpiece and cutting torch, both of which can cause fire. When using a plasma arc torch, wear approved safety glasses with side shield to protect eyes. Answers A, B, and C are incorrect because all of these safety precautions should be taken when using a plasma arc torch.

The correct answer is A. Answer A is correct because Technician A only is correct. Technician B is incorrect because if no leaks are found, the regulator screws should be turned counterclockwise to drain the hose. Answers C and D are incorrect because only Technician A is correct.

The correct answer is B. Answer B is correct because Technician B only is correct. To adjust the oxygen working pressure, a Technician should open the oxygen torch needle valve and proceed in the same manner as in adjusting the fuel-gas pressure. Technician A is incorrect because the fuel-gas pressure is adjusted by opening the torch needle valve and turning the fuel-gas regulator screw clockwise. Adjust the regulator to the working pressure needed for the particular tip size, and then close the torch needle valve. Answers C and D are incorrect because only Technician B is correct.

The correct answer is A. Answer A is correct because neutral will usually have no chemical effect on the metal being welded and will not oxidize the weld metal. Neutral will also not cause an increase in the carbon content of the weld metal. A neutral flame is used for most welding operations and for preheating during cutting operations. Answers B and C are incorrect because the settings would not be hot enough for cutting. Answer D is incorrect because rose bud tip is used for general heating of metal or brazing and not used for cutting.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because cuts that are improperly made will produce ragged and irregular edges with adhering slag at the bottom of the metal plate. Technician B is also correct because there is a wide variety of cutting tip styles and sizes available to suit various types of work. The thickness of the material to be cut generally governs the selection of the tip. The cutting oxygen pressure, cutting speed, and preheating intensity should be controlled to produce narrow, parallel sided kerfs. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because Technician A only is correct. Many front-wheel drive vehicles often use a flexible header pipe to accommodate engine vibrations and twisting motions. Technician B is incorrect because a Y-pipe is only used on V-type engines that have two banks of cylinders such as a V6 or V8 engine. Answers C and D are incorrect because only Technician A is correct.

The correct answer is B. Answer B is correct because a single exhaust with catalytic converter is shown. Answers A, C, and D are incorrect because these configurations are not shown.

The correct answer is D. Answer D is correct because low oil pressure is least likely to cause high exhaust back pressure. Answer A is incorrect because use of an improper muffler will likely cause excessive back pressure. Answer B is incorrect because excessive carbon will likely cause excessive back pressure. Answer C is incorrect because a collapsed exhaust pipe will likely cause excessive back pressure.

The correct answer is B. Answer B is correct because the exhaust manifold is shown. Answers A, C, and D are incorrect because these components are not shown.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because a leaking intake manifold gasket can allow a vacuum leak that can cause a misfire leading to a rough idle condition. Technician B is also correct because a cracked exhaust manifold can affect engine operation by changing the oxygen sensor signal, which affects fueling and it makes a clicking or tapping sound that sounds like a valve lifter noise. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is D. Answer D is correct because the 2 ¼ inch ID is the correct measurement. The technician will need to increase the ID size just enough to slide over the second pipe. Answers A and B are incorrect because these are being measured in OD instead of ID. Answer C is incorrect because this would be too large to make a proper seal on the connection.

The correct answer is B. Answer B is correct because checking for clearance is most important when installing a new system. Answer A is incorrect because some hangers may still be usable. Answer C is incorrect because the header pipe is generally bolted. Answer D is incorrect because the backpressure would more than likely be within vehicle specifications.

The correct answer is C. Answer C is correct because the tool shown is used to cut exhaust pipe. Answers A, B, and D are incorrect because the tool shown is not used to cut these components.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because the tap test and done to see if the brick inside the converter is loose or if the muffler is rusted through internally. Technician B is also correct because all exhaust component should be properly positioned before tightening the clamps and hangers. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is D. Answer D is correct because a DEF (Diesel Exhaust Tank) Tank is part of a Diesel engine exhaust aftertreatment system. Answers A, B, and C are incorrect because they are all components of an exhaust system.

The correct answer is A. Answer A is correct because Technicians commonly use WD-40™ to loosen and remove rusted nuts and bolts. Answers B, C, and D are incorrect because WD-40™ is not intended to be used on the components listed.

The correct answer is D. Answer D is correct and the exception because a breaker bar is not typically used when replacing a catalytic converter. Answers A, B, and C are incorrect because they are all common tools used when replacing a catalytic converter.

The correct answer is C. Answer C is correct because the bolts should be installed at a 90-degree angle or right-angle to prevent them from inadvertently contacting the ground. Answers A, B, and D are incorrect because the other positions can cause interference.

The correct answer is B. Answer B is correct because only Technician B is correct. Cutting a pipe before the weld point is the proper procedure for separating an exhaust pipe that has been welded to a muffler. Technician A is incorrect because an exhaust pipe should not be cut after the weld point. Answers C and D are incorrect because only Technician B is correct.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because a broken transmission mount could cause the exhaust system to hit the floor pan. Technician B is also correct because a broken engine mount could cause the exhaust system to ground against the frame. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is B. Answer B is correct because silicone spray is an excellent preservative. Answer A is incorrect because WD-40 should only be used on metal. Answers C and D are incorrect because they should not be used to preserve the rubber parts of an exhaust hanger.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because is reduced turbocharger boost pressure could be caused by excessive exhaust backpressure. Technician B is also correct turbine speed is dependent on the pressure drop between the turbine inlet and outlet. High exhaust pressure reduces the pressure differential across the turbine which causes turbocharger speed and boost pressure to fall. Backpressure is generated by the mufflers and is the process of eliminating engine exhaust noise. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is D. Answer D is correct because inserting a scratch awl into the exhaust seams is the exception and is not a normal troubleshooting procedure. Answers A, B and C are incorrect because they are all common ways to locate a leak in an exhaust system.

The correct answer is C. Answer C is correct because both Technicians are correct. Technician A is correct because when the check valve fails, hot exhaust can travel into and destroy the switching valve(s) and air pump itself. On a cold engine before the oxygen sensor is hot enough to reach closed loop, the air flow is directed to the exhaust manifold (s) through one-way check valve(s). These valves keep exhaust gases from entering the switching solenoids and the air pump itself. Technician B is also correct because a check valve contains a spring-type metallic disc or reed that closes the air line under exhaust back pressure. A restricted catalytic converter can cause excessive back pressure and push the disc or reed open allowing exhaust gasses enter and destroy the switching. Answers A, B, and D are incorrect because both Technicians are correct.

The correct answer is A. Answer A is correct because the converter Original Equipment Manufacturers (OEMs) either provide such a statement with the converter or have an example in their catalogs. All OEM converters come with or give access to this document. Answers B, C and D are incorrect because the listed resources do not typically provide this document.

The correct answer is A. Answer A is correct because Technician A is correct. A replacement catalytic converter must be Installed in the same location as the original. Technician B is incorrect because the same type of converter as the original must be installed. Converter information is sometimes available on the emissions emission’s label or from the online service information or OEM parts information. Answers C and D are incorrect because only technician A is correct.

The correct answer is A. Answer A is correct because installing a converter test pipe to reduce backpressure replaces the catalytic converter, voids the manufactures warranty, and is illegal. Answers B, C and D are incorrect because are all repairs that are acceptable to perform.

The correct answer is A. Answer A is correct because penalties for EPA emissions standards violations by individuals, service or repair shops, or fleet operators can be up to $2,500 per violation. Each improper installation is considered a separate violation. Additionally, new-car dealers can be penalized up to $25,000 per violation of EPA emissions standards. Any individual who violates EPA emissions standards could be subject to the same penalty as an automotive Technician. Answers B, C and D are incorrect because they are not the penalties for EPA emissions standards violations by individuals, service or repair shops, or fleet operators.

The correct answer is D. Answer D is correct because documenting the disposal location is the exception and is not required by Federal or local EPA standards. The Technician should follow the Federal and local disposal method which more than likely is to recycle the converter. Answers A, B and C are incorrect because the reasons listed are required documentation.

The correct answer is B. Answer B is correct because a Repair Order must be retained for 6 months. Converters that have been replaced must also be kept for 15 days (converters must be identified or marked to indicate the car they came from). The most significant difference between states is the length of time needed to keep documentation. Answers A, C and D are incorrect because they are not accurate statements.

The correct answer is B. Answer B is correct because carbon monoxide (CO) is created during combustion. If there is enough oxygen available, carbon in the fuel should be converted to carbon dioxide (CO2). A lack of oxygen in the combustion changer produces incomplete combustion and creates CO rather than CO2. Answers A, C and D are incorrect because they are not the most dangerous and poisonous pollutant found in a vehicle’s exhaust.

The correct answer is D. Answer D is correct because the EGR commanded position value should be 100% and not 0%. Answers A, B and D are incorrect because they are all true statements regarding the operation of the Composite Vehicle System.

The correct answer is A. Answer A is correct because only Technician A is correct. Some state inspection laws will not allow modification of the exhaust system from factory standards. A larger exhaust may not allow enough backpressure to operate a backpressure EGR valve which will cause the vehicle to fail the emission test. Technician B is incorrect because some state inspection laws will not allow modification of the exhaust system from factory standards. Answers C and D are incorrect because only Technician A is correct.

The correct answer is B. Answer B is correct because installing a general 3-way converter is correct and the exception. The Technician must install the same type of converter as the original (oxidation, 3-way, or 3-way-plus oxidation (dual-bed)). This information is sometimes available on the emissions label or from the manufacturer’s application catalog. Answer A is correct because a converter should be installed in the same location as the original. Answer C is correct because the proper converter should always be used, as determined and specified by the converter manufacturer. Answer D is correct because the converter must always be connected to any existing air injection components.

The correct answer is B. Answer B is correct because backpressure is the resistance to exhaust gas flow in an automotive exhaust system. Increasing the ability of a high-performance exhaust system to collect and discharge gas is often an important element in improving engine performance. Answers B, C and D are incorrect because they do not describe the resistance to exhaust gas flow in an automotive exhaust system.

The correct answer is D. Answer D is correct and the exception because high exhaust backpressure will not lead to low exhaust emissions but will lead to high exhaust emissions from temperatures caused by inadequate flow of fresh cool air intake charge over the exhaust valve, especially during valve overlap period. Overheating of cooling systems caused by transfer of heat energy from slow-moving exhaust gases lingering near the exhaust ports into the cylinder head. Excessive crankcase pressure that can result from exhaust gas pressure retained in the cylinder that will leak past piston rings and enter the crankcase. Exhaust backpressure therefore contributes to increased volume of engine blow-by. Answers A, B and C are incorrect because they can be the cause of high exhaust backpressure.

The correct answer is C. Answer C is correct because an air management valve is shown in the above photo. Answers A, B, and D are incorrect because each are components that are not shown in the above photo.