ASE L1
Questions and Answers
- 1.
All of the cylinders in an overhead cam engine have low compression. What is the MOST LIKELY cause of this condition?
- A.
Burned valves
- B.
Leaking head gasket
- C.
Worn piston rings
- D.
Broken timing belt
Correct Answer
D. Broken timing beltExplanation
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.Rate this question:
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- 2.
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?
- A.
Technician A Only
- B.
Technician B Only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
B. Technician B OnlyExplanation
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.Rate this question:
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- 3.
A customer complains that their vehicle lacks power. What would be the the first step in determining the cause of the problem?
- A.
Analyze scan data
- B.
Measure fuel pressure
- C.
Road test the vehicle
- D.
Check exaust backpressure
Correct Answer
C. Road test the vehicleExplanation
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.Rate this question:
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- 4.
A engine pings excessively under load. All of the following conditions could cause this condition EXCEPT:
- A.
Missing thermostat
- B.
Improper antifreeze concentration
- C.
EGR valve stuck closed
- D.
Missing catalytic converter
Correct Answer
A. Missing thermostatExplanation
A missing thermostat can cause an engine to run cool or cold, which can lead to excessive pinging under load. This is because the engine may not reach its optimal operating temperature, causing the fuel mixture to be too lean and leading to detonation or pinging. The other conditions listed, such as improper antifreeze concentration, a stuck closed EGR valve, and a missing catalytic converter, can all contribute to excessive pinging under load.Rate this question:
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- 5.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 6.
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?
- A.
Tecnician A
- B.
Technician B
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 7.
The fuel control system on the composite vehicle remains in open loop at all times. Technician A says that this could be the result of poor connection at ECM terminal 60. Technician B says that a faulty IAT sensor could be the problem. Who is right?
- A.
Tehnican A
- B.
Technican B
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Both Technician A and Technician B are not right. The statement in the question states that the fuel control system on the composite vehicle remains in open loop at all times. This means that the system does not rely on inputs from sensors like the ECM terminal 60 or the IAT sensor to adjust the fuel mixture. Therefore, neither Technician A's suggestion of a poor connection at ECM terminal 60 nor Technician B's suggestion of a faulty IAT sensor would be the cause of the open loop operation.Rate this question:
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- 8.
Once a zirconia oxygen sensor reaches operating temperature, how quickly should it respond to changes in the air/fuel ratio?
- A.
50 microseconds
- B.
100 milliseconds
- C.
One second
- D.
1000 milliseconds
Correct Answer
B. 100 millisecondsExplanation
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.Rate this question:
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- 9.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
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.Rate this question:
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- 10.
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?
- A.
The engine is running lean
- B.
Sensor switching frequency is too slow
- C.
Sensor response time is below normal
- D.
The sensor is functioning properly
Correct Answer
D. The sensor is functioning properlyExplanation
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.Rate this question:
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- 11.
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%
- A.
EGR valve not seating
- B.
Faulty ignition coil
- C.
Clogged injector
- D.
Vacuum lean
Correct Answer
A. EGR valve not seatingExplanation
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.Rate this question:
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- 12.
All of the following statements regarding the schematic shown above are true EXCEPT:
- A.
The solenoid coil receives battery power at KOEO and KOER
- B.
A blown 20A fuse would result in 0 volts at ECM terminal 23
- C.
The EGR valve is shown in the de-energized state
- D.
The pintle position sensor is shown at approximately the 2.5V position
Correct Answer
B. A blown 20A fuse would result in 0 volts at ECM terminal 23Explanation
If a 20A fuse is blown, it would result in an open circuit, meaning no current can flow through it. As a result, there would be no voltage at ECM terminal 23, contradicting the statement.Rate this question:
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- 13.
The composite vehicle won't shift into third gear. Technician A says that an open NO. 2 shift solenoid (SS2) could be the problem. Technician B says tat a poor connection at TCM terminal 75 could cause this condition. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
Both Technician A and Technician B are correct. An open NO. 2 shift solenoid (SS2) can cause the composite vehicle to not shift into third gear. Additionally, a poor connection at TCM terminal 75 can also cause this condition. Therefore, both Technician A and Technician B's statements are accurate in identifying potential causes for the problem.Rate this question:
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- 14.
All of the following statements regarding the composite vehicle's OBD II monitors are true EXCEPT:
- A.
The Comprehensive Component Monitor is a one-trip test
- B.
The Fuel Control, O2 Sensor and Misfire Monitors are run continuously
- C.
The EVAP Monitor will not run if engine temperature is above 94 degree F (34 degree C)
- D.
A LTFT reading of -30% could cause the Fuel Control Monitor to fail
Correct Answer
B. The Fuel Control, O2 Sensor and Misfire Monitors are run continuouslyExplanation
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.Rate this question:
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- 15.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 16.
Refer to the schematic below to answer the following question: Technician A says that to check the voltage drop across the main relay switch contacts, the voltmeter leads should be connected between terminals B and D with there relay energized. Technician B says that to check the voltage drop in the O2 ground circuit, the voltmeter leads should be connected between PCM terminals B15 and G101. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
A. Technician A onlyExplanation
Technician A is correct because to check the voltage drop across the main relay switch contacts, the voltmeter leads should be connected between terminals B and D with the relay energized. Technician B's statement about checking the voltage drop in the O2 ground circuit is not relevant to the question and therefore incorrect.Rate this question:
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- 17.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
A. Technician A onlyExplanation
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.Rate this question:
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- 18.
The following waveform was captured in closed loop at 2000 rpm from the HO2S 1/2 sensor on the composite vehicle. Technician A says that the waveform could be the result of a unintentional ground in the purge flow control circuit (Terminal 37 of the ECM). Technician B says that a clogged PCV valve may be generating this pattern. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Without any additional information or analysis of the waveform, it is not possible to determine the cause of the waveform or which technician is correct. The given answer states that neither Technician A nor Technician B is right, indicating that both of their explanations are incorrect.Rate this question:
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- 19.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 20.
The engine in the composite vehicle will ot start. A preliminary diagnosis indicates thath there is o spark. Technician A says that a defective CMP sensor could be the root cause of the problem. Technician B says that the ignition module should be replaced. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Neither Technician A nor Technician B is correct. The preliminary diagnosis states that there is no spark, which means that the problem lies with the ignition system. Technician A suggests that a defective CMP sensor could be the cause, but the CMP sensor is responsible for detecting the position of the camshaft and does not directly affect the ignition system. Technician B suggests replacing the ignition module, but without further information or testing, it cannot be determined if the ignition module is indeed faulty. Therefore, neither technician's suggestion is the correct solution for the problem.Rate this question:
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- 21.
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?
- A.
The CKP sensor is faulty.
- B.
The reluctor has a chipped tooth
- C.
The CKP sensor is misadjusted
- D.
The patter is normal
Correct Answer
B. The reluctor has a chipped toothExplanation
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."Rate this question:
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- 22.
All of the following could cause an engine with waste spark ignition to misfire EXCEPT:
- A.
Low prmary circuit resistance
- B.
Faulty generator
- C.
Open plug wire
- D.
Defective ignition control module
Correct Answer
A. Low prmary circuit resistanceExplanation
Low primary circuit resistance refers to the resistance in the primary circuit of the ignition system. A low resistance in this circuit can cause the ignition coil to overheat and fail, resulting in a misfire. Therefore, low primary circuit resistance can cause an engine with waste spark ignition to misfire.Rate this question:
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- 23.
The composite vehicle fails a loaded mode I/M test for excessive hydrocarbons. Which of the following is the root cause of the problem?
- A.
Shorted CMP signal wire to the ECM
- B.
Open CKP sensor
- C.
Poor connection at ECM terminal 12
- D.
Blown fuse no. 4
Correct Answer
C. Poor connection at ECM terminal 12Explanation
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.Rate this question:
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- 24.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
B. Technician B onlyExplanation
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.Rate this question:
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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?
- A.
7500Ώ
- B.
11MΏ
- C.
1.5Ώ
- D.
8.25kΏ
Correct Answer
D. 8.25kΏExplanation
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.Rate this question:
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- 26.
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?
- A.
Faulty regulator
- B.
Restricted fuel return line
- C.
Defective pump
- D.
Leaking injector
Correct Answer
A. Faulty regulatorExplanation
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.Rate this question:
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- 27.
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
- A.
Lack of power
- B.
High CO emissions
- C.
Rough idle
- D.
Hard start
Correct Answer
B. High CO emissionsExplanation
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.Rate this question:
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- 28.
A kinked vacuum line to hte fuel pressure regulator could cause:
- A.
Long engine crank times
- B.
Poor fuel economy
- C.
High NOx emisions
- D.
An off-idle hesitation
Correct Answer
B. Poor fuel economyExplanation
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.Rate this question:
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- 29.
All of the following statements concerning the composite vehicle's fuel system are false EXCEPT:
- A.
The system is a contiuous return design
- B.
Fuel pressure ranges between 45 at idle to 50 at wide-open throttle
- C.
Pressure should be at least 45 psi immediately following engine shutdown
- D.
The injectors are "bank fired"
Correct Answer
C. Pressure should be at least 45 psi immediately following engine shutdownExplanation
The given statement "Pressure should be at least 45 psi immediately following engine shutdown" is true.Rate this question:
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- 30.
Two technicians are discussing the injector waveform shown above. Technician A says that the waveform is typical of a peak and hold injector. Technician B says that the rise in control circuit voltage is normal. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Neither Technician A nor Technician B is right. The question does not provide enough information to determine the accuracy of their statements. The waveform alone cannot confirm whether it is typical of a peak and hold injector, and the rise in control circuit voltage being normal or not cannot be determined without further context or specifications. Therefore, it is not possible to determine who is right based on the given information.Rate this question:
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- 31.
The composite vehicle has no fuel pressure. Technician A says that the problem could be the result of a blown No. 3 fuse. Technician B says that the problem could be a poor connection at ECM terminal 5. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
A. Technician A onlyExplanation
Technician A is correct. The composite vehicle having no fuel pressure could indeed be the result of a blown No. 3 fuse. This fuse is responsible for providing power to the fuel pump, and if it is blown, the fuel pump will not receive power and therefore will not be able to generate fuel pressure. Technician B's suggestion of a poor connection at ECM terminal 5 is not relevant to the issue of fuel pressure, so Technician B is not correct in this case.Rate this question:
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- 32.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
A. Technician A onlyExplanation
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.Rate this question:
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- 33.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 34.
All the following condition could cause an increase in hydrocarbon emissions EXCEPT:
- A.
Missing air pump drive belt
- B.
EGR valbe Stuck closed
- C.
EVAP system leak
- D.
EGR valve not seating
Correct Answer
B. EGR valbe Stuck closedExplanation
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.Rate this question:
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- 35.
The composite vehicle has and illuminated MIL and a stored DTC for and EVAP system failure. Which of the following could be the cause?
- A.
Blown fuse No. 4
- B.
Gas cap is too tight
- C.
Canister vent solenoid resistance is 49 ohms
- D.
Poor connection at ECM terminal 36
Correct Answer
D. Poor connection at ECM terminal 36Explanation
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.Rate this question:
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- 36.
the composite vehicle idles rough and stalls when the transmission is put into gear. Technician A says that the throttle body may be contaminated. Technician B says that the circuit to ECM terminal 35 could be shorted to ground. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
Both Technician A and Technician B are correct. The rough idle and stalling when the transmission is put into gear can be caused by a contaminated throttle body, as mentioned by Technician A. This is because a contaminated throttle body can restrict the airflow and disrupt the proper functioning of the engine. Additionally, Technician B's suggestion that the circuit to ECM terminal 35 could be shorted to ground is also valid. A short circuit in this circuit can disrupt the communication between the throttle body and the engine control module (ECM), leading to rough idle and stalling. Therefore, both technicians are correct in their assessments.Rate this question:
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- 37.
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?
- A.
Poor cold driveability
- B.
Spark knock
- C.
Lack power
- D.
Excessive NOx emissions
Correct Answer
A. Poor cold driveabilityExplanation
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.Rate this question:
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- 38.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
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.Rate this question:
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- 39.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
B. Technician B onlyExplanation
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.Rate this question:
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- 40.
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?
- A.
The converter was damaged as a result of the CO failure
- B.
The tecnician damaged the EGR vacuum line while making the initial repair
- C.
The CO failure masked the NOx problem
- D.
The failed retest was coincidental
Correct Answer
C. The CO failure masked the NOx problemExplanation
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.Rate this question:
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- 41.
What is the most effective way to test the PCV system?
- A.
Shake th valve to see if it rattles
- B.
Perform a vacuum draw test
- C.
Perform an rpm drop test
- D.
Measure the vacuum signal at the valve
Correct Answer
B. Perform a vacuum draw testExplanation
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.Rate this question:
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- 42.
Two technicians are discussing the effect air injection has on the carbon dioxide and oxygen readings from a properly functioning vehicle. Technician A says that CO2 reaches is highest point with the air injection system enabled. Technician B says that disabling the air injection system will cause an increase in the O2 reading. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Both Technician A and Technician B are incorrect. The effect of air injection on the carbon dioxide and oxygen readings from a properly functioning vehicle is not mentioned or explained in the question. Therefore, it is not possible to determine who is right.Rate this question:
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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
- A.
Clogged PCV valve
- B.
Faulty pressure regulator
- C.
Restricted fuel return line
- D.
Egr valve not seating
Correct Answer
D. Egr valve not seatingExplanation
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.Rate this question:
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- 44.
Technician A says that an engine misfire will result in low CO along with high O2 readings. Technician B says that low CO and high O2 readings could be the sign of a lean mixture. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
C. Both A and BExplanation
Both Technician A and Technician B are correct. An engine misfire can result in low CO (carbon monoxide) readings because when a misfire occurs, the fuel is not burned completely, leading to a decrease in CO emissions. Additionally, a lean mixture, which refers to an insufficient amount of fuel in the air-fuel mixture, can also cause low CO and high O2 (oxygen) readings.Rate this question:
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- 45.
All of the following information is typically entered into the computer prior to performing an I/M test EXCEPT:
- A.
GCWR
- B.
Emissions equipment (based on underhood emissions label)
- C.
VIN
- D.
Engine size
Correct Answer
A. GCWRExplanation
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.Rate this question:
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- 46.
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?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
B. Technician B onlyExplanation
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.Rate this question:
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- 47.
A vehicle with throttle body injection failed the ASMK5015 test based on the following Vehicle Inspection Report (VIR). Mode CO% HC ppm Loaded Limit Reading Result Limit Reading Result ASN5015 0.44 1.32 FAIL 7.8 23.6 FAIL NOx PPM RPM Dilution Limit Reading Result Reading Reading 62.5 37.9 PASS 152.8 12.10% Technician A says that the gas readings could be the result of a bad catalytic converter. Technician B says that the engine may have a leaking throttle body gasket. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
A. Technician A onlyExplanation
Technician A is more likely to be correct. The elevated CO% and HC ppm readings are indicative of incomplete combustion, which can be associated with a faulty catalytic converter. Technician B's suggestion of a leaking throttle body gasket is less likely to cause high CO% and HC levels.Rate this question:
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- 48.
A TSI test is automatically aborted after 10 seconds in the high speed mode. Refer to the test results to determine the validity of the technicians statements. 2500 RPM Test Results Measured Limit HC (ppm) 4 220 CO (%) 0.00 1.2 CO2 (%) 0.00 O2 (%) 20.85 Engine RPM 2558 Technician A says that thee exhaust system may be leaking. Technician B says that the engine could be running too lean. Who is right?
- A.
Technician A only
- B.
Technician B only
- C.
Both A and B
- D.
Neither A or B
Correct Answer
D. Neither A or BExplanation
Based on the given test results, neither Technician A nor Technician B is right. Technician A suggests that the exhaust system may be leaking, but there is no evidence of high levels of HC or CO in the test results, which would indicate a leak. Technician B suggests that the engine could be running too lean, but the test results do not show any abnormal levels of CO2 or O2. Therefore, both technicians' statements are not supported by the test results, and neither A nor B is correct.Rate this question:
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- 49.
The composite vehicle failed an I/M 240 test for excessive NOx. Which of the following conditions could be causing the problem?
- A.
Weak EGR diagphragm spring
- B.
Stuck open thermostat
- C.
Clogged EGR supply tube
- D.
Leaking injector
Correct Answer
C. Clogged EGR supply tubeExplanation
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.Rate this question:
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- 50.
What conclusion can be drawn from the I/M 240 inspection report shown below?
- A.
The vehicle passed
- B.
The vehicle failed for high HC
- C.
The vehicle failed for high NOx
- D.
The vehicle failed for high HC and CO
Correct Answer
C. The vehicle failed for high NOxExplanation
The conclusion that can be drawn from the I/M 240 inspection report is that the vehicle failed the inspection due to high NOx emissions.Rate this question:
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Aug 02, 2024Quiz Edited by
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Apr 15, 2012Quiz Created by
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