ASE L2 Exam Questions

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81.

Technician A states that nozzle injectors are used on vehicles with an injection pump setup. Technician B states that nozzle injectors are used on vehicles with a fuel distributor.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Nozzle type fuel injectors are used on systems with an injection pump or a fuel distributor because they cannot create enough pressure on their own. The alternative to nozzle type fuel injectors is the unit injectors, which don't require an injection pump because the injector creates enough pressure for operation.

82.

How many wires does a typical ECT sensor have?

  • Two

  • Three

  • Four

  • Five

Correct answer: Two

A typical engine coolant temperature (ECT) sensor has two wires — there's typically a voltage wire and a ground wire. The ECT is a resistor that is temperature variable and usually has a negative temperature coefficient.

83.

Which type of sensor is a typical throttle position sensor? 

  • Mechanically variable resistor

  • A pressure sensor

  • Negative coefficient thermistor

  • A solid state resistor

Correct answer: Mechanically variable resistor

A throttle position sensor is typically a three-wire mechanically variable resistor. Resistors can only function as a resistor when placed under a load.

An example of a negative coefficient thermistor is a typical coolant temperature sensor, while a pressure sensor can be a typical manifold pressure sensor. An example of a solid state resistor is a typical blower motor module/resistor.

84.

Technician A states that blue smoke indicates that oil is being burned in the combustion chamber. Technician B states that blue smoke is a sign of low engine compression.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

Blue smoke exists when oil is being burned. It can be caused by a bad turbocharger seal, a worn valve guide, or defective piston rings.

Low engine compression leads to unburned fuel, which causes white smoke from the exhaust. White smoke can also be caused by non-working or faulty injectors, and when the engine temperature doesn't get hot enough.

85.

Technician A states that oil leaking past the turbocharger seals can set an exhaust temperature code. Technician B states that an exhaust temperature code can be set by a defective catalytic converter.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

When oil leaks past the turbocharger seals, the catalytic converter has to work harder. The same condition occurs if there's a leaking or damaged wastegate. Whenever the catalytic converter has to work harder, the exhaust temperature code can set, so technician A is correct.

If the catalytic converter is defective, an exhaust temperature code can set, so technician B is also correct.

86.

All of these statements about the exhaust after treatment system are true, except:

  • To clean soot from the DPF, it must be removed from the truck

  • Its job is to convert soot to ash

  • To clean ash from the DPF, it must be removed from the truck

  • The ECM relies on the differential pressure sensor to monitor restrictions with the DPF

Correct answer: To clean soot from the DPF, it must be removed from the truck

There's no soot to clean from the DPF. All of the soot is converted into ash during the regeneration event. This process occurs within the filter.

The DPF does covert the soot to ash, and it may need to be removed to clean out the ash. Additionally, the ECM is responsible for monitoring preessure drop with the differential pressure sensor.

87.

Using the composite vehicle on the ASE website, answer the following question:

With the key on and engine off and with a DMM hooked between the negative battery terminal and terminal 4 of the PM sensor with the meter set to voltage, what should the reading approximately be?

  • 0 volts

  • 5 volts

  • 12 volts

  • 16 volts

Correct answer: 0 volts

The meter is set between two ground circuits, and the voltage should be around zero. Connecting to pin 3 would read 12 volts.

88.

Using the composite vehicle on the ASE website, answer the following question:

A technician is performing forced regeneration of the DPF. The following temperatures are recorded 15 minutes after starting regeneration:

  • EGT1 = 650 °F
  • EGT2 = 900 °F
  • EGT3 = 950 °F

Which of the following statements is true?

  • All EGTs are normal

  • EGT1 is lower than usual

  • EGT2 is higher than usual

  • EGT3 is higher than usual

Correct answer: All EGTs are normal

All EGTs appear to be normal. EGT1 would be the lowest temperature, with EGT2 and EGT3 reading similarly.

An abnormal reading would be above 1100 °F.

89.

Using the composite vehicle on the ASE website, answer the following question:

How many power feeds does the ECM have?

  • Three

  • Two

  • Four

  • Five

Correct answer: Three

There are three fused power feeds to the ECM. Fuses 11,12, and 61 power the ECM.

The other fuses aren't directly connected to the ECM.

90.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that the DEF supply pump relay coil resistance should read 80 ohms. Technician B states that the coil resistance of the DEF supply pump relay should be 92 ohms.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The coil resistance of the DEF supply pump relay is 90 ± 4 Ω. Therefore, any reading between 86 and 94 ohms is considered normal.

The DEF supply pump relay receives power from the ECM and sends voltage to the DEF supply pump.

91.

What test can be used to determine if a fuel system problem is electronic or mechanical?

  • Injector click test

  • Fuel pressure test

  • Vacuum leak test

  • Fuel pump flow test

Correct answer: Injector click test

To figure out if the fuel system issue is electronic or mechanical, technicians should perform an injector click test. If the injector doesn't click during the test, it's an electronic problem.

If the injector clicks, it's a mechanical problem. However, mechanical problems can be within the injector or cylinder, such as with low compression.

92.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that a fuel injector should be replaced if the measured resistance is 3.5 ohms. Technician B states a fuel injector should be replaced if the measured resistance is 0.4 ohms.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

The fuel injector coil resistance specifications are 2 Ω ± 0.5 Ω, meaning a normal reading would be between 1.5 and 2.5 ohms. If the readings are outside of the specification, the injector needs to be replaced.

Technician A is correct because the reading is too high, while technician B is correct because the reading is too low.

93.

Technician A states that a cylinder cutout test can pinpoint a compression issue. Technician B states that a cylinder cutout test can pinpoint an injector issue.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

A cutout test can show which cylinder has an issue, but it cannot pinpoint what is wrong with a cylinder. After determining the cylinder, other tests will need to be performed to pinpoint the fault.

The cutout test is equivalent to a power balance test. It's going to reveal what cylinder is having trouble without giving the cause.

94.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that the DEF system heaters receive battery voltage from the DEF supply pump relay. Technician B states that the heaters are needed to keep the DEF in a liquid state.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

DEF system heaters receive battery voltage from the DEF heater relay. Heaters are located in the tank, pump, and lines.

The purpose of the DEF system heaters is to keep the DEF in a liquid state.

95.

Using the composite vehicle on the ASE website, answer the following question:

What action occurs two minutes after the low coolant indicator comes on if the coolant is severely low?

  • Shutdown

  • No action

  • Warning

  • Derate

Correct answer: Shutdown

Two minutes after the low coolant indicator, the engine will shut down if the coolant level is not adjusted. There are three levels of protection: warning, derate, and shutdown.

No action will only occur if the coolant indicator is not on and the system is working as designed. At the first sign of low coolant, a warning is issued. After that, the system derates power to protect the engine from wear.

96.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that the amber check engine light (CEL) comes on when the engine enters derate (limp) mode. Technician B states that a solid red stop engine lamp (SEL) occurs when the engine is in shutdown mode.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

As part of the engine protection system, the amber check engine light (CEL) will come on when the engine goes into derate mode, making technician A correct.

Technician B is incorrect because shutdown mode causes the red stop engine lamp (SEL) to flash. It doesn't come on solid.

97.

Technician A states that if a cylinder becomes disabled, engine speed will drop significantly. Technician B states that an ECM can compensate for a disabled cylinder to maintain engine speed.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

If a cylinder becomes disabled, the ECM can compensate for it, making technician B correct. The ECM compensates by increasing the pulse of the other injectors to maintain engine speed.

The defective cylinder can be found by performing an injector cutout test.

98.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that an open circuit at terminal 372 at the ECM will cause an inlet air temp sensor DTC. Technician B states that an open circuit at terminal 372 at the ECM will cause a fuel temp sensor DTC to set.

Who is correct?

  • Technician A 

  • Technician B

  • Both A and B 

  • Neither A nor B

Correct answer: Technician A

Terminal 372 is the ground for the air inlet temperature sensor. If there's an open circuit at terminal 372, a DTC will set for the inlet air temperature sensor, making technician A correct.

The fuel temperature sensor circuits are completely separate and would not be affected, making technician B incorrect. They are located at terminals 369 and 370.

99.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that the low pressure fuel supply pump is mechanical. Technician B states that the low pressure fuel supply pump is electronic.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The low pressure fuel supply pump is a mechanical pump that is driven by the high pressure fuel pump. It delivers fuel to the high pressure pump and the exhaust aftertreatment system.

The low pressure supply fuel pump provides 40 PSI of pressure at test port B with the key on and engine cranking.

100.

Using the composite vehicle on the ASE website, answer the following question:

Technician A states that the EGR differential pressure sensor has a maximum reading of 40 PSI. Technician B states that the EGR differential pressure sensor has a maximum reading of 5 PSI.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The EGR differential pressure sensor is a low reading sensor that varies from 0-5 PSI/0–35 kPa. These are the maximum values that will be displayed with diagnostic equipment hooked to the composite vehicle.