ASE L1

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  • 1/80 Questions

    Oxides of Nitrogen emissions are controlled by the catalytic converter and the:

    • PCV system
    • EFE system
    • EGR system
    • Secondayr air system
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About This Quiz

The ASE L1 quiz assesses knowledge in engine diagnostics, focusing on issues like low compression, power loss, and fuel injection problems. It evaluates technical skills vital for automotive professionals, aligning with ASE standards.

Automotive Technology Quizzes & Trivia

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  • 2. 

    A customer complains that their vehicle lacks power. What would be the the first step in determining the cause of the problem?

    • Analyze scan data

    • Measure fuel pressure

    • Road test the vehicle

    • Check exaust backpressure

    Correct Answer
    A. Road test the vehicle
    Explanation
    The first step in determining the cause of the problem when a customer complains that their vehicle lacks power would be to road test the vehicle. This involves taking the vehicle for a drive to observe its performance and behavior firsthand. By doing so, a technician can assess factors such as acceleration, engine responsiveness, and any abnormal noises or vibrations. This initial road test provides valuable information that can help narrow down potential causes and guide further diagnostic procedures.

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  • 3. 

    The usual number of terminating resistors on a CAN harness is:

    • One

    • Two

    • Three

    • Four

    Correct Answer
    A. Two
    Explanation
    The usual number of terminating resistors on a CAN harness is two. Terminating resistors are used to eliminate signal reflections and ensure proper signal transmission on a CAN bus. Placing a terminating resistor at each end of the bus helps to match the impedance of the bus and prevent signal distortion. Having two terminating resistors, one at each end, ensures optimal signal quality and reduces the risk of communication errors on the CAN network.

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  • 4. 

    A cylinder leakage test is being performed on an overhead valve v8 engine.  When air is applied to the No. 5 cylinder, a hissing noise is heard from the tailpipe. Technician A says that the cam lobe for the No. 5 exaust valve could be worn down. Technician B says that the No 5 exaust valve could be burnt.  Who is right?

    • Technician A Only

    • Technician B Only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B Only
    Explanation
    Technician B is correct. A hissing noise from the tailpipe during a cylinder leakage test indicates that there is a problem with the exhaust valve. This could be caused by a burnt exhaust valve, which would prevent it from sealing properly and allowing air to escape. Technician A's suggestion of a worn down cam lobe would not cause a hissing noise from the tailpipe. Therefore, only Technician B is correct in this scenario.

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  • 5. 

    Once a zirconia oxygen sensor reaches operating temperature, how quickly should it  respond to changes in the air/fuel ratio?

    • 50 microseconds

    • 100 milliseconds

    • One second

    • 1000 milliseconds

    Correct Answer
    A. 100 milliseconds
    Explanation
    A zirconia oxygen sensor should respond to changes in the air/fuel ratio within 100 milliseconds. This means that once the sensor reaches its operating temperature, it is able to detect and react to changes in the air/fuel mixture within a relatively short period of time. This quick response time is important for the sensor to accurately measure the oxygen levels in the exhaust gases and provide feedback to the engine control unit for optimal fuel combustion.

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  • 6. 

    The composite vehicle failed an I/M 240 test for excessive NOx.  Which of the following conditions could be causing the problem?

    • Weak EGR diagphragm spring

    • Stuck open thermostat

    • Clogged EGR supply tube

    • Leaking injector

    Correct Answer
    A. Clogged EGR supply tube
    Explanation
    A clogged EGR (Exhaust Gas Recirculation) supply tube can cause excessive NOx (nitrogen oxides) emissions in a composite vehicle. The EGR system is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce combustion temperatures and lower NOx emissions. If the supply tube is clogged, it can restrict the flow of exhaust gases into the intake manifold, leading to higher combustion temperatures and increased NOx emissions. Therefore, a clogged EGR supply tube could be causing the excessive NOx emissions observed in the failed I/M 240 test.

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  • 7. 

    Oxides of Nitrogen begins to form when combustion temperatures exceed:

    • 1500° F

    • 2000° F

    • 2500° F

    • 3000° F

    Correct Answer
    A. 2500° F
    Explanation
    Oxides of Nitrogen begin to form when combustion temperatures exceed 2500° F. At this temperature, the high energy of the combustion process causes nitrogen and oxygen molecules in the air to react and form various nitrogen oxides, such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). These oxides of nitrogen are harmful pollutants that contribute to air pollution and can have negative effects on human health and the environment.

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  • 8. 

    The default throttle position on the composite vehicle is:

    • 0%

    • 15%

    • 20%

    • 30%

    Correct Answer
    A. 15%
    Explanation
    The default throttle position on the composite vehicle is set at 15%. This means that when the vehicle is started or the throttle is not being actively controlled, it will be positioned at 15% open. This allows for a small amount of power to be delivered to the engine, enabling the vehicle to idle or move at a slow speed without the need for constant acceleration input from the driver.

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  • 9. 

    Two technician are discussing catalytic converters and their effect on emissions and performance.  Technician A says a defective converter will always cause reduced performance.  Technician B says a defective catalytic converter can cause high emissions without reducing performance.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B only
    Explanation
    Technician B is correct. A defective catalytic converter can cause high emissions without reducing performance. This is because a faulty converter may not efficiently convert harmful gases into less harmful substances, leading to increased emissions. However, the converter's impact on performance may vary depending on the specific issue with the converter.

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  • 10. 

    When performing a drive cycle on the composite vehicle, which of the following is required?

    • Start with a warm engine

    • Keep vehicle speed below 50 MPH

    • Fuel tank must be between 1/4 and 3/4 full

    • Immediate shutdowns with no idle periods

    Correct Answer
    A. Fuel tank must be between 1/4 and 3/4 full
    Explanation
    During a drive cycle on a composite vehicle, it is required to have the fuel tank between 1/4 and 3/4 full. This is important to ensure accurate testing and measurement of the vehicle's performance and emissions. Having the fuel tank within this range provides a consistent fuel level that allows for reliable data collection and analysis. It helps to eliminate any potential variations in performance that may occur due to different fuel levels.

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  • 11. 

    All of the following information is typically entered into the computer prior to performing an I/M test EXCEPT:

    • GCWR

    • Emissions equipment (based on underhood emissions label)

    • VIN

    • Engine size

    Correct Answer
    A. GCWR
    Explanation
    The GCWR (Gross Combined Weight Rating) is not typically entered into the computer prior to performing an I/M (Inspection and Maintenance) test. The GCWR refers to the maximum allowable weight of a fully loaded vehicle and its trailer, and it is not directly related to emissions or engine performance. The other options - emissions equipment, VIN (Vehicle Identification Number), and engine size - are commonly entered into the computer as they provide important information for conducting the I/M test.

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  • 12. 

    On the composite vehicle, the Immobilizer Module will do all of the following EXCEPT:

    • Stop operation of the starter motor

    • Verify the key code

    • Disable injectors if the keycode is invaled

    • Recognize the ECM ID number

    Correct Answer
    A. Stop operation of the starter motor
    Explanation
    The Immobilizer Module is responsible for verifying the key code, disabling injectors if the keycode is invalid, and recognizing the ECM ID number. However, it does not directly stop the operation of the starter motor.

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  • 13. 

    The composite vehicle has high emissions and an illuminated Malfunction Indicator Light (MIL).  The downstream oxygen sensor voltage is varying consistent with the upstream oxygen sensors.  Technician A says a faulty catalytic converter could be the problem.  Technician B says the downstream oxygen sensor could be defective.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. A faulty catalytic converter can cause high emissions and trigger the Malfunction Indicator Light (MIL) to illuminate. The varying voltage of the downstream oxygen sensor, consistent with the upstream oxygen sensors, indicates that the catalytic converter may not be functioning properly. Technician B's suggestion that the downstream oxygen sensor could be defective does not explain the high emissions and illuminated MIL.

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  • 14. 

    All of the cylinders in an overhead cam engine have low compression.  What is the MOST LIKELY cause of this condition?

    • Burned valves

    • Leaking head gasket

    • Worn piston rings

    • Broken timing belt

    Correct Answer
    A. Broken timing belt
    Explanation
    The MOST LIKELY cause of low compression in all cylinders of an overhead cam engine is a broken timing belt. This can lead to a loss of synchronization between the camshaft and crankshaft, resulting in improper valve timing and insufficient compression in all cylinders.

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  • 15. 

    Idle speed is too high on an engine with a speed density fuel injection system.  Technician A says that someone may have replaced the PCV valve with the wrong type.  Technician B says that a leaking throttle body gasket may be causing the problem.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct.
    Technician A is correct because if the PCV valve is replaced with the wrong type, it can cause an imbalance in the air-fuel mixture, resulting in a higher idle speed.
    Technician B is also correct because a leaking throttle body gasket can cause a vacuum leak, which can lead to a higher idle speed.
    Therefore, both technicians are correct in their explanations for the high idle speed on an engine with a speed density fuel injection system.

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  • 16. 

    A vehicle with multiport fuel injection stalls on deceleration. Technician A says the problem could be the result of a faulty TCC solenoid.  Technician B says that a contaminated throttle body may be the cause.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct. A faulty TCC solenoid can indeed cause a vehicle with multiport fuel injection to stall on deceleration. The TCC solenoid is responsible for engaging and disengaging the torque converter clutch, and if it is faulty, it may not disengage properly, causing the engine to stall. Additionally, a contaminated throttle body can also cause stalling on deceleration. If the throttle body is dirty or clogged, it can restrict the airflow to the engine, leading to stalling. Therefore, both Technician A and Technician B are correct in their assessment of the potential causes of the problem.

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  • 17. 

    A kinked vacuum line to hte fuel pressure regulator could cause:

    • Long engine crank times

    • Poor fuel economy

    • High NOx emisions

    • An off-idle hesitation

    Correct Answer
    A. Poor fuel economy
    Explanation
    A kinked vacuum line to the fuel pressure regulator can restrict the flow of fuel to the engine, leading to poor fuel economy. When the fuel pressure is not regulated properly, the engine may receive less fuel than required, resulting in decreased efficiency and increased fuel consumption. This can lead to lower mileage and higher fuel costs.

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  • 18. 

    The ISC motor toggles back and forth at closed throttle on an overhead valve V8 with DI ignition.  A permanent magnet sensor inside the distributor is used to generate the rpm signal.  Technician A says that a loose timing change may be causing the problem technician B says that the problem may be the result of a worn distributor shaft gear.  Who is right?

    • Tecnician A

    • Technician B

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct. A loose timing chain can cause the ISC motor to toggle back and forth at closed throttle, as it can affect the timing of the engine. Additionally, a worn distributor shaft gear can also cause this issue, as it can affect the accuracy of the rpm signal generated by the sensor inside the distributor. Therefore, both possibilities should be considered when diagnosing the problem.

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  • 19. 

    The composite vehicle has an unstable idle, the MIL is on, and DTC P0300 is stored for a Random Misfire.  According to the scan data, which of the following could be the root cause of the problem? ECT 198° F                 IAT 86° F                    MAF 0.2V                   APP 1 0.5V MAP/BARO  2.3V        LOOP CLOSED        TAC 15%                   BAT 13.2V        APP 2 1.5V                  RPM 513                     HO2S 1/1 0.86         HO2S 2/1 0.78 HO2S ½ 0.51              TP 1 4.50V                  TP 2 0.5V                    Bank 1 STFT               Bank 2 STFT               Bank 1 LTFT               Bank 2 LTFT    -12%                                -9%                             -8%                                -5%    

    • EGR valve not seating

    • Faulty ignition coil

    • Clogged injector

    • Vacuum lean

    Correct Answer
    A. EGR valve not seating
    Explanation
    The EGR valve not seating could be the root cause of the problem because an improperly seated EGR valve can cause an unstable idle and trigger a random misfire. The EGR valve is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce emissions. If the valve is not seating properly, it can disrupt the air-fuel mixture and cause misfires. This can also trigger the MIL (Malfunction Indicator Lamp) to turn on and store a DTC (Diagnostic Trouble Code) P0300 for a random misfire.

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  • 20. 

    All of the following will disable the air conditioner compressor clutch on the composite vehicle EXCEPT:

    • A shorted A/C request switch

    • An open circuit at pin B of the A/C pressure sensor

    • An open circuit at pin A of the A/C pressure sensor

    • An open circuit at pin 5 of the ECM

    Correct Answer
    A. A shorted A/C request switch
    Explanation
    An open circuit at pin B of the A/C pressure sensor, an open circuit at pin A of the A/C pressure sensor, and an open circuit at pin 5 of the ECM will all disable the air conditioner compressor clutch on the composite vehicle. However, a shorted A/C request switch will not disable the clutch as it will constantly send a signal to engage the compressor.

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  • 21. 

    On the composite vehicle the CAN terminating resistors are located

    • In the CAN harness

    • In the TCM and the instrument cluster

    • In the ECM and the immobilizer module

    • In the ECM and the Instrument Cluster

    Correct Answer
    A. In the ECM and the Instrument Cluster
    Explanation
    The correct answer is in the ECM and the Instrument Cluster. CAN terminating resistors are used to prevent signal reflections and ensure proper communication in a CAN network. In this case, the terminating resistors are located in both the ECM (Engine Control Module) and the Instrument Cluster of the composite vehicle. This means that these two components have the necessary circuitry to terminate the CAN bus and maintain signal integrity.

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  • 22. 

    The A/C clutch is inoperable on the composite vehicle.  Technician A says an open circuit to ECM pin 27 could be the problem.  Technician B says this condition could be due to a refrigerant leak.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Niether A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. An open circuit to the ECM (Engine Control Module) pin 27 could indeed be a possible cause of the A/C clutch being inoperable. This is because ECM pin 27 likely controls the signal to the A/C clutch relay, and if there's an open circuit, the signal won't reach the relay, preventing the clutch from engaging.
    Technician B's suggestion that a refrigerant leak could be the cause of the A/C clutch issue is not directly related to the electrical circuit problem described by Technician A, so Technician B's statement is not relevant to the given scenario.

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  • 23. 

    The composite vehicle fails on I/M 240 test due to high carbon monoxide emissions.  HC is barely within limits, while NOx is well below the maximum cutpoint.  Once the cause of the high CO has been corrected, the vechile is retested and fails again, only this time for excessive NOx.  What is the MOST likely reason for the subsequent failure?

    • The converter was damaged as a result of the CO failure

    • The tecnician damaged the EGR vacuum line while making the initial repair

    • The CO failure masked the NOx problem

    • The failed retest was coincidental

    Correct Answer
    A. The CO failure masked the NOx problem
    Explanation
    The CO failure masked the NOx problem means that the high levels of carbon monoxide emissions were covering up the fact that there was also a problem with excessive nitrogen oxide emissions. This means that when the cause of the high carbon monoxide was fixed and the vehicle was retested, the true issue with the excessive NOx became apparent and caused the subsequent failure.

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  • 24. 

    The composite vehicle fails a loaded mode I/M test for excessive hydrocarbons.  Which of the following is the root cause of the problem?

    • Shorted CMP signal wire to the ECM

    • Open CKP sensor

    • Poor connection at ECM terminal 12

    • Blown fuse no. 4

    Correct Answer
    A. Poor connection at ECM terminal 12
    Explanation
    A poor connection at ECM terminal 12 can cause the composite vehicle to fail a loaded mode I/M test for excessive hydrocarbons. This poor connection may disrupt the communication between the ECM and other components, leading to incorrect fuel mixture and increased hydrocarbon emissions.

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  • 25. 

    The ignition coils on the composite vehicle are being tested with and ohmmeter.  Which of the following readings is within the specifications for the secondary winding?

    • 7500Ώ

    • 11MΏ

    • 1.5Ώ

    • 8.25kΏ

    Correct Answer
    A. 8.25kΏ
    Explanation
    The correct answer is 8.25kΏ. The secondary winding of the ignition coils should have a resistance within the specified range. The reading of 8.25kΏ falls within this range, indicating that the secondary winding is functioning properly.

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  • 26. 

    A Vehicle fails an I/M 240 test for excessive NOx emissions.  Technician A says that a restricted air filter may be causing the  problem.  Technician B says that the engine may have excessive intake valve deposits.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B only
    Explanation
    Technician B is correct. Excessive intake valve deposits can lead to incomplete combustion and higher NOx emissions. A restricted air filter, on the other hand, can affect the air-fuel mixture, but it is less likely to cause excessive NOx emissions. Therefore, Technician B's explanation is more relevant to the given scenario.

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  • 27. 

    On the comp;osite vehiclle all of the folowing are required to engage the Torque Converter Clutch EXCEPT:

    • Shift solenoid No. 1 engaged

    • Transmission temperature at 150° F

    • Vehicle speed over 40 MPH

    • Transmission in 3rd or 4th gear

    Correct Answer
    A. Shift solenoid No. 1 engaged
    Explanation
    The shift solenoid No. 1 engaged is not required to engage the Torque Converter Clutch. The Torque Converter Clutch is typically engaged when the vehicle is in 3rd or 4th gear, the transmission temperature is at 150° F, and the vehicle speed is over 40 MPH. The shift solenoid No. 1 is responsible for controlling the shift between 1st and 2nd gear, but it is not directly related to the engagement of the Torque Converter Clutch.

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  • 28. 

    The EFE heater stays energized all the time on an engine with TBI.  Which of the following symptoms would not be associated with this condition?

    • Poor cold driveability

    • Spark knock

    • Lack power

    • Excessive NOx emissions

    Correct Answer
    A. Poor cold driveability
    Explanation
    If the EFE (Early Fuel Evaporation) heater stays energized all the time on an engine with TBI (Throttle Body Injection), it means that the heater will be continuously heating the fuel mixture, even when the engine is cold. This continuous heating will ensure that the engine gets a rich fuel mixture, which is beneficial for cold start conditions. Therefore, poor cold driveability would not be associated with this condition, as the continuous heating of the fuel mixture would actually improve the engine's performance during cold starts.

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  • 29. 

    Fuel pressure on a continuous return injection system is within specifications, but leaks down to zero immediately after the pump stops running.  What is the most likely cause of this condition?

    • Faulty regulator

    • Restricted fuel return line

    • Defective pump

    • Leaking injector

    Correct Answer
    A. Faulty regulator
    Explanation
    The most likely cause of the fuel pressure dropping to zero immediately after the pump stops running is a faulty regulator. The regulator is responsible for maintaining a consistent fuel pressure by controlling the flow of fuel returning to the fuel tank. If the regulator is faulty, it may not be able to properly regulate the fuel pressure, causing it to drop to zero when the pump stops running.

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  • 30. 

    A vehicle with multi-port fuel injection only starts with the throttle held open.  A review of the vehicle history indicates that all though the vehicle has 75,000 miles, on it, the engine has never been serviced except for an occasional oil change.  The MFI system uses an idle Air Control Valve to regulate closed throttle rpm.  Technician A says that IAC valve may be stuck in the fully extended position.  Technician B says that the problem may be the result of a clogged fuel filter.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. The fact that the vehicle only starts with the throttle held open suggests that the idle air control valve (IAC valve) may be stuck in the fully extended position. The IAC valve is responsible for regulating the closed throttle RPM in a multi-port fuel injection system. If it is stuck, it can prevent the vehicle from starting properly. Technician B's suggestion of a clogged fuel filter is not relevant to the given symptom of the vehicle only starting with the throttle held open.

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  • 31. 

    What is the most effective way to test the PCV system?

    • Shake th valve to see if it rattles

    • Perform a vacuum draw test

    • Perform an rpm drop test

    • Measure the vacuum signal at the valve

    Correct Answer
    A. Perform a vacuum draw test
    Explanation
    Performing a vacuum draw test is the most effective way to test the PCV system. This test involves using a vacuum gauge to measure the amount of vacuum being drawn by the system. By connecting the gauge to the PCV valve, any leaks or blockages in the system can be detected. This test provides a more comprehensive assessment of the PCV system's functionality compared to the other options listed.

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  • 32. 

    Refer to the graphic below to answer the following question: The CKP waveform shown above was taken from the composite vehicle during cranking.  Which of the following best describes the waveform?

    • The CKP sensor is faulty.

    • The reluctor has a chipped tooth

    • The CKP sensor is misadjusted

    • The patter is normal

    Correct Answer
    A. The reluctor has a chipped tooth
    Explanation
    The given CKP waveform shows a clear irregularity in the pattern, indicating that there is a chipped tooth on the reluctor. This irregularity can cause incorrect readings from the CKP sensor, leading to faulty engine timing and performance. Therefore, the correct answer is "The reluctor has a chipped tooth."

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  • 33. 

    Two technicians are discussing emission controls and related failure symptoms.  Technician A says that if the hot air hose is missing on an engine with a thermostatic air cleaner.  NOx emissions will be higher than normal.  Technician B says that a faulty secondary air system can cause backfiring.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B only
    Explanation
    Technician B is correct. A faulty secondary air system can cause backfiring. However, Technician A is incorrect in stating that if the hot air hose is missing on an engine with a thermostatic air cleaner, NOx emissions will be higher than normal.

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  • 34. 

    The composite vehicle is running poorly and has a flashing MIL.  Technician A says a broken circuit to ECM pin 9 could be the cause.  Technician B says the condition could be due to and open fuse number 4.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. A flashing MIL (Malfunction Indicator Lamp) indicates a severe misfire that can cause damage to the catalytic converter. A broken circuit to ECM (Engine Control Module) pin 9 can disrupt the communication between the ECM and the ignition system, leading to a misfire. Technician B's suggestion of an open fuse number 4 is not relevant to the issue of a flashing MIL and poor running condition.

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  • 35. 

    The composite vehicle lacks power.  The engine has been recently tuned up and results from a power balance test were good.  The following snapshot of scan data was captured at 2500 rpm under no-load.  Which analysis of this information is correct? ECT 209° F                 IAT 86° F                    MAF 0.3V                   APP 1 0.65V MAP/BARO  3.6V        LOOP CLOSED       TAC 21%                    DTC NONE     APP 2 1.65V               RPM 2500                 HO2S 1/1 0.89            HO2S 2/1 0.91 HO2S ½ 0.56              TP 1 4.25V               TP 2 0.88V                  Bank 1 STFT               Bank 2 STFT               Bank 1 LTFT               Bank 2 LTFT     -13%                           -15%                           -10%                               -12%   Technician A says that the root cause of the problem may be clogged catalytic converter.  Technician B says that the problem could be the result of low fuel pressure.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct because a clogged catalytic converter can cause a lack of power in the vehicle. The scan data shows that the Bank 1 and Bank 2 Short Term Fuel Trim (STFT) values are both negative, indicating that the engine is running rich. This could be a result of a clogged catalytic converter, as it can restrict the exhaust flow and cause the engine to run inefficiently. Technician B's suggestion of low fuel pressure does not align with the provided scan data, as there are no indications of fuel pressure issues.

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  • 36. 

    All the following condition could cause an increase in hydrocarbon emissions EXCEPT:

    • Missing air pump drive belt

    • EGR valbe Stuck closed

    • EVAP system leak

    • EGR valve not seating

    Correct Answer
    A. EGR valbe Stuck closed
    Explanation
    An EGR valve stuck closed would not cause an increase in hydrocarbon emissions. The EGR valve is responsible for recirculating a portion of the exhaust gases back into the intake manifold to reduce the formation of nitrogen oxides (NOx). If the valve is stuck closed, it would prevent the recirculation of exhaust gases, but it would not directly contribute to increased hydrocarbon emissions.

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  • 37. 

    An engine with DI ignition becomes harder to start as outside temperature drops.  Below freezing, the engine will not start at all.  Technician A says that the problem could be a faulty ignition coil.  Technician B says that the coil wire may be bad.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct. An engine with DI (Direct Ignition) ignition becomes harder to start as the outside temperature drops because lower temperatures can affect the performance of the ignition system. Technician A suggests that a faulty ignition coil could be the problem, which is a plausible explanation as a faulty coil can lead to weak or no spark, making it difficult for the engine to start. Technician B suggests that the coil wire may be bad, which is also a valid possibility as a damaged or worn-out coil wire can result in a weak or intermittent spark, causing starting issues. Therefore, both technicians are correct in their assessments.

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  • 38. 

    A DTC P0420 (Low Catalyst Efficiency) is stored in memory on a vehicle with an illuminated MIL.  Technician A says that the root cause of the problem may be worn valve guide seals.  Technician B says that a leaking Exhaust system may have triggered the DTC.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct. A DTC P0420 code indicates low catalyst efficiency, which can be caused by multiple factors. Technician A is correct in suggesting that worn valve guide seals could be a potential root cause of the problem. These seals can allow oil to enter the combustion chamber, leading to increased emissions and decreased catalyst efficiency. Technician B is also correct in suggesting that a leaking exhaust system could trigger the DTC. A leak in the exhaust system can cause abnormal readings from the oxygen sensors, leading to a false low catalyst efficiency code. Therefore, both technicians are correct in their assessments.

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  • 39. 

    The composite vehicle stalls when shifted into a drive range, but restarts immediately.  Technician A says the wire to pin 72 of the TCM is shorted to ground.  Technician B says an open fuse 72 could be the cause.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. The composite vehicle stalls when shifted into a drive range and immediately restarts, indicating a problem with the wire to pin 72 of the TCM being shorted to ground. This short circuit could be causing the stall and immediate restart. Technician B's suggestion of an open fuse 72 does not explain the symptoms described.

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  • 40. 

    The wave form shown above was captured in closed loop at 1500 rpm from the Bank 1 O2 sensor on the composite vehicle.  What can be determined by an analysis of the waveform?

    • The engine is running lean

    • Sensor switching frequency is too slow

    • Sensor response time is below normal

    • The sensor is functioning properly

    Correct Answer
    A. The sensor is functioning properly
    Explanation
    Based on the given information, the waveform captured from the Bank 1 O2 sensor on the composite vehicle indicates that the sensor is functioning properly.

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  • 41. 

    The composite vehicle has and illuminated MIL and a stored DTC for and EVAP system failure.  Which of the following could be the cause?

    • Blown fuse No. 4

    • Gas cap is too tight

    • Canister vent solenoid resistance is 49 ohms

    • Poor connection at ECM terminal 36

    Correct Answer
    A. Poor connection at ECM terminal 36
    Explanation
    A poor connection at ECM terminal 36 could be the cause of the illuminated MIL and stored DTC for an EVAP system failure. A poor connection at this terminal could result in a loss of communication or faulty signals between the ECM (Engine Control Module) and the EVAP system components. This could lead to the MIL (Malfunction Indicator Lamp) being illuminated and a DTC (Diagnostic Trouble Code) being stored in the system, indicating a failure in the EVAP system.

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  • 42. 

    The composite vehicle will not start.  Cranking speed is above 250 rpm.  The following PIDs were observed by two technicians under KOEO conditions at closed throttle. ECT 68° F                   IAT 67° F        MAF 0.2V                   APP 1 0.5V MAP/BARO 101 kPa            LOOP OPEN     TAC 35%                    BAT 11.9V        APP 2 1.5V                 RPM 0             HO2S 1/1 0.00            HO2S 2/1 0.00 HO2S ½ 0.00              TP 1 4.50V      TP C 0.5V                   FUEL PUMP OFF Tank LEV 0%              TR P/N            LOAD 0%       Technician A says that the system is stuck in the clear flood mode.  Technician B says that a fault MAP sensor may be the cause of the no-start.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Neither A or B
    Explanation
    Neither Technician A nor Technician B is correct. The given information does not indicate that the system is stuck in the clear flood mode. Additionally, while a faulty MAP sensor can cause a no-start condition, there is no evidence in the provided data to suggest that the MAP sensor is the cause of the issue. Therefore, both technicians' explanations are incorrect.

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  • 43. 

    A vehicle with continuous return injection fails the low-speed portion of a two-speed idle test.  According to the test results, which of the following conditions caused the vehicle to fail? Idle Test Results                                       Measured                     Limit HC (ppm)                    855                              220 CO (%)                        0.14                             1.2 CO2 (%)                      7.98 O2 (%)                         4.85                 Engine RPM               648     

    • Clogged PCV valve

    • Faulty pressure regulator

    • Restricted fuel return line

    • Egr valve not seating

    Correct Answer
    A. Egr valve not seating
    Explanation
    The vehicle failed the low-speed portion of the two-speed idle test because the EGR valve is not seating properly. This means that the EGR valve is not closing properly during idle, causing an excessive amount of exhaust gas to enter the combustion chamber. As a result, the levels of HC (hydrocarbons) and CO (carbon monoxide) in the exhaust are higher than the allowed limits. The other options (clogged PCV valve, faulty pressure regulator, restricted fuel return line) do not directly affect the EGR valve or the levels of HC and CO in the exhaust.

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  • 44. 

    The composite vehicle uses two Throttle Position Sensors.  Technician A says this is a failsafe in case one sensor fails.  Technician B says that the use of two sensors allows for a more accurate measurement of throttle position.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B only
    Explanation
    Technician B is correct. The use of two throttle position sensors in a composite vehicle allows for a more accurate measurement of throttle position. Having two sensors provides redundancy, ensuring that if one sensor fails, the other can still provide accurate data. This redundancy improves the reliability and safety of the vehicle's throttle system. Technician A's statement about the failsafe in case one sensor fails is incorrect as it does not accurately explain the purpose of having two sensors.

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  • 45. 

    Two technicians are discussing the merits of a snap throttle test for evaluating ignition system performance.  Technician A says that this test is more useful for port-injected engines than it is on veheicle with throttle body injection.  Technician B says that using a spark tester is more effective way to test the ignition system.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician B only
    Explanation
    Technician B is correct. Using a spark tester is a more effective way to test the ignition system. The snap throttle test is not specifically designed to evaluate ignition system performance, but rather to evaluate the response of the engine's air/fuel mixture to sudden changes in throttle position. A spark tester, on the other hand, directly checks for the presence of spark in the ignition system, providing a more accurate assessment of its performance.

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  • 46. 

    The composite vheicle has poor performance.  Technician A says a faulty intake cam position solenoid could be the problem.  Technician B says a faulty exhaust cam position solenoid could be the cause.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Technician A only
    Explanation
    Technician A is correct. A faulty intake cam position solenoid can indeed cause poor performance in a composite vehicle. The intake cam position solenoid is responsible for controlling the timing of the intake valves, which affects the engine's performance. If the solenoid is faulty, it may not be able to properly regulate the timing, leading to poor performance. On the other hand, Technician B's statement about the faulty exhaust cam position solenoid is not relevant to the given situation and does not address the issue of poor performance.

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  • 47. 

    All of the following statements regarding the composite vehicle's OBD II monitors are true EXCEPT:

    • The Comprehensive Component Monitor is a one-trip test

    • The Fuel Control, O2 Sensor and Misfire Monitors are run continuously

    • The EVAP Monitor will not run if engine temperature is above 94 degree F (34 degree C)

    • A LTFT reading of -30% could cause the Fuel Control Monitor to fail

    Correct Answer
    A. The Fuel Control, O2 Sensor and Misfire Monitors are run continuously
    Explanation
    The Comprehensive Component Monitor (CCM) is not a one-trip test; it monitors all components and systems that provide input or receive output signals from the powertrain control module (PCM) continuously while the vehicle is running. The other statements are correct: the Fuel Control, O2 Sensor, and Misfire Monitors run continuously, the EVAP Monitor will not run if the engine temperature is above 94 degrees F (34 degrees C), and a Long Term Fuel Trim (LTFT) reading of -30% could cause the Fuel Control Monitor to fail.

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  • 48. 

    The readings shown below were recorded during an injector balance test.  All of the following symptoms are consistent with the test results EXCEPT: Injector  1 2 3 4 5 6   Initial Pressure 55 55 55 55 55 55   Final Pressure 32 46 33 49 31 34   Pressure Drop 23 9 22 6 24 21 spec (psi) 21-24

    • Lack of power

    • High CO emissions

    • Rough idle

    • Hard start

    Correct Answer
    A. High CO emissions
    Explanation
    Based on the given readings, all of the symptoms listed (lack of power, rough idle, hard start) are consistent with the test results except for high CO emissions. CO emissions are typically high when there is incomplete combustion of fuel, which can be caused by factors such as a rich fuel mixture or a faulty oxygen sensor. However, the pressure drop readings for all the injectors are within the specified range of 21-24 psi, indicating that the injectors are balanced and delivering the correct amount of fuel. Therefore, high CO emissions would not be expected in this scenario.

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  • 49. 

    The composite vehicle fails a two-speed idle test due to excessive carbon monoxide.  When the PCV valve is removed from the valve cover, CO emissions drop below the maximum allowable limit.  Technician A says that this test proves the PCV system is working properly.  Technician B says that the engine may have one or more leaking injectors.  Who is right?

    • Technician A only

    • Technician B only

    • Both A and B

    • Neither A or B

    Correct Answer
    A. Both A and B
    Explanation
    Both Technician A and Technician B are correct.

    Technician A is correct because when the PCV valve is removed and the CO emissions drop below the maximum allowable limit, it indicates that the PCV system is working properly. The PCV valve is responsible for removing harmful gases, including carbon monoxide, from the engine and redirecting them to the intake manifold for combustion.

    Technician B is also correct because excessive carbon monoxide emissions could be caused by one or more leaking injectors. Leaking injectors can lead to an imbalance in the air-fuel mixture, resulting in incomplete combustion and higher CO emissions.

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Quiz Review Timeline (Updated): Aug 2, 2024 +

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  • Current Version
  • Aug 02, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Apr 15, 2012
    Quiz Created by
    Mike239
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