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Quiz Session - Attempts With Random Questions

ASE L1 Exam Questions

Page 9 of 10

161.

When should a canister vent solenoid be closed?

  • During evaporative emissions (EVAP) system leak testing

  • Under heavy load

  • At idle

  • At cruise speed 

Correct answer: During evaporative emissions (EVAP) system leak testing

The canister vent solenoid is a normally open solenoid. The only time the solenoid should be closed is during EVAP system leak testing. 

162.

What gas does a five-gas analyzer read that a four-gas analyzer does not?

  • NOx

  • HC

  • CO2

  • O2

Correct answer: NOx

A five-gas analyzer is needed for NOx emission problems. A four-gas analyzer reads HC, O2, CO, and CO2. 

163.

Which of the following is often used as the primary input to the ECM for fuel injector sequencing? 

  • Camshaft position sensor

  • Accelerator pedal position (APP) sensor

  • Throttle position sensor 

  • Oxygen sensor 

Correct answer: Crankshaft sensor 

In a sequential fuel injector system, the injectors are fired one at a time, according to the spark plug firing order. This requires the ECM to receive a cylinder identification signal to initiate injector sequencing. This signal is typically provided by either the crankshaft position sensor or the camshaft position sensor. 

The accelerator pedal position (APP) sensor, throttle position sensor, and oxygen sensor provide no input that alters the sequential fuel injector system control. 

164.

All the following could be caused by a faulty secondary air injection system, EXCEPT:

  • Increased NOx emissions 

  • An overheated catalytic converter 

  • Poor fuel economy 

  • Illuminated MIL

Correct answer: Increased NOx emissions

Secondary air injection promotes catalytic converter efficiency and helps reduce CO and HC emissions. However, it does not play a role in limiting NOx emissions. 

A faulty secondary air injection system would not affect NOx output, but it could cause all the other problems listed. 

165.

In an OBD II DLC, how many of the 16 cavities are common to all vehicles?

  • 7 cavities

  • 2 cavities

  • 10 cavities

  • 12 cavities

Correct answer: 7 cavities

According to OBD II regulations, seven cavities of the DLC are common to all vehicles. The other nine are manufacturer-specific. 

166.

Technician A says the manifold vacuum should read 18-20 in. Hg with the engine at idle. Technician B says when connected to a ported vacuum source at closed throttle, the vacuum gauge should read near 0 in. Hg. 

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Both technicians are correct. When reading a manifold vacuum with an engine in good running order, the gauge should remain between 18-20 in. Hg while at idle.

Using a vacuum gauge connected to a ported vacuum source with the engine at closed throttle should always produce a reading of near 0 in. Hg. 

167.

Technician A says excessive oil consumption can result in catalytic converter damage. Technician B says a damaged catalytic converter can lead to increased HC emissions. 

Who is correct? 

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Both technicians are correct. Excessive HC emissions result in engine damage, no matter if the root cause is excessive oil consumption, unburnt fuel, or blow-by. After repairing the initial cause of increased HC emissions, a damaged converter can continue to output an excessive level. 

168.

In the open loop, the composite vehicle determines fuel injector pulse width on which two signals?

  • MAF and ECT 

  • MAP and ECT

  • CKP and ECT

  • TP and ECT

Correct answer: MAF and ECT

In the open loop, the composite vehicle determines injector pulse width based on input from the MAF (mass air flow) and ECT (engine coolant temperature). The system remains in an open loop until 10 seconds have passed since the engine start-up and the throttle position is lower than 80%. 

Once in a closed loop, it bases injector pulse width on signals from the air/fuel ratio sensors. 

169.

A technician is checking the air/fuel ratio sensor 1 (AFRS 1/1) performance on the composite vehicle. What does a reading of 4.3 volts indicate?

  • Lean air/fuel mixture of 20:1

  • Rich air/fuel mixture of 12:1

  • Lambda 0.75

  • Perfectly balanced air/fuel mixture of 14:7:1

Correct answer: Lean air/fuel mixture of 20:1

When the air/fuel ratio sensors on the composite vehicle read 4.3 volts, that indicates a lean air/fuel mixture of 20:1 (Lambda 1.36). When the sensors read 1.3 volts, that indicates a rich air/fuel mixture of 11:1 (Lambda 0.75).

A perfectly balanced air/fuel mixture would be 14:7:1, or 2.5 volts. 

170.

Voltage drop tests should be run in which of the following conditions?

  • KOER (Key On Engine Running)

  • KOEO (Key On Engine Off)

  • Without the key in the ignition

  • Any condition

Correct answer: KOER (Key On Engine Running)

A voltage drop test measures the difference in voltage between two points in a live circuit. 

Voltage drop tests should always be run with the key in the ignition and the engine running. If not, excessive voltage drop may not be noticed. 

171.

A large EVAP leak is one greater than what value? 

  • 0.040 inches

  • 0.050 inches

  • 0.020 inches

  • 0.030 inches

Correct answer: 0.040 inches

Vacuum decay is used to check for large evaporative emissions (EVAP) leaks, which are those greater than 0.040 in. Specific criteria for the large leak test include a specific engine temperature, fuel level, and ambient air temperature with the engine running. 

172.

Technician A says all vehicles are equipped with a PCV valve. Technician B says all vehicles are equipped with a crankcase ventilation system. 

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

Not all vehicles are equipped with a positive crankcase ventilation valve. However, all vehicles do have some type of crankcase ventilation system to reduce blowby and crankcase pressure. 

With some vehicles, the crankcase vapors are drawn through a fixed-metering orifice. 

173.

Which of the following is required for a small EVAP leak detection test to run on the composite vehicle?

  • Ambient air temperature between 40 and 105 degrees Fahrenheit 

  • Vehicle driven for at least 10 minutes prior

  • Fuel level between 1/4 tank and full

  • Coolant temperature above 120 degrees Fahrenheit

Correct answer: Ambient air temperature between 40 and 105 degrees Fahrenheit 

For an evaporative emissions (EVAP) small leak detection test to run, the fuel tank must be between 1/4 and 3/4 full, the ambient air temperature must be between 40 and 105 degrees Fahrenheit, and the vehicle must have been driven for 15 to 90 minutes prior to the test. 

There's no restriction on coolant temperature for the test. 

174.

The air/fuel ratio for a vehicle is 10:1 at all speeds during an emissions test. What is the MOST likely symptom the vehicle might display? 

  • Sulfur odor

  • High-speed misfire

  • Overheating 

  • Detonation 

Correct answer: Sulfur odor

A ratio of 10:1 indicates the engine is running very rich. A common symptom of a rich-running engine is sulfur odor. 

Other symptoms may include black smoke, hesitation, surging, poor fuel economy, stalling, a rough idle, and the engine failing to reach operating temperatures. 

175.

A vehicle has the following I/M results at idle: 100 ppm HC, 0.3% CO, 12% CO2, and 2.5% O2. 

What does this indicate?

  • The catalytic converter is not warmed up.

  • The engine has a misfire.

  • The analyzer probe is not fully inserted into the exhaust.

  • There's a bad O2 sensor.

Correct answer: The catalytic converter is not warmed up.

These readings indicate the engine is cold, and the catalytic converter is not warmed up enough for thorough testing. 

176.

Technician A says the composite vehicle uses a continuous return fuel system. Technician B says the fuel pump in the composite vehicle is duty-cycle controlled. 

Who is correct? 

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

Only technician B is correct. In the composite vehicle, the fuel pump is duty-cycle controlled by the fuel pump control module. 

Technician A is wrong because the composite vehicle has a returnless fuel system. 

177.

Technician A says a leaking fuel injector will cause the firing kV portion of an ignition waveform pattern to be higher. Technician B says a leaking fuel injector will cause the burn time portion of an ignition waveform pattern to be shorter. 

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

Both technicians are wrong. Firing kV and burn time are inversely proportional. A leaking fuel injector will cause a rich condition, which will reduce secondary resistance. As a result, firing kV will be lower, and burn time will be longer. 

178.

Technician A says a lean air/fuel mixture will allow the catalytic converter to be more efficient at reducing NOx. Technician B says a rich air/fuel mixture will allow the catalytic converter to be more efficient at reducing HC. 

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

Both technicians are wrong. A lean air/fuel mixture will allow the catalytic converter to be more efficient at reducing HC and CO. However, a lean air/fuel mixture will also result in increased NOx created by the high combustion temperatures. The opposite is true when the air/fuel mixture is rich. 

179.

For the composite vehicle, a fault in the throttle actuator motor circuit will result in the throttle opening being reduced or increased to what percentage? 

  • 15%

  • 20%

  • 10%

  • 30%

Correct answer: 15%

The composite vehicle uses a bidirectional pulse-width modulated DC motor to control the position of the throttle plate. In the event of a motor circuit problem, the control module will reduce or increase throttle opening to 15%. 

When the TAC is disabled, the value on the scan tool will show 15%.

180.

Technician A says low compression will increase HC. Technician B says low compression will decrease CO. 

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Both technicians are correct. Low compression will result in incomplete combustion and increased HC emissions. CO emissions will generally be slightly decreased.

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