ASE L2 Exam Questions

Page 2 of 15

21.

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

How many pins are there for the data link connector on the public network?

  • Nine

  • Three

  • Five

  • Seven

Correct answer: Nine

On the public network, the diagnostic tool communicates with the modules through a nine-pin connector for information retrieval and software updates. The public network data link connector is found in the cab.

The private network data link connector only has three pins. This connector is found in the engine compartment.

22.

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

Technician A states that the transmission gear position sensor is located on the transmission top plate. Technician B states that the transmission gear position sensor delivers voltage to the ECM.

Who is correct?

  • Technician A 

  • Technician B

  • Both A and B

  • Neither A nor b

Correct answer: Technician A

The transmission gear position sensor is located on the transmission top plate. It is a non-adjustable potentiometer that monitors the positioning of the transmission gear selector motor.

The signal from the transmission gear position sensor is sent to the TCM. It delivers a signal between 0.5 to 4.5 V.

23.

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

What is the minimum engine cranking speed to start the engine?

  • 200 RPM

  • 150 RPM

  • 250 RPM

  • 300 RPM

Correct answer: 200 RPM

The minimum engine cranking speed needed to start is 200 RPM. The starter is responsible for this process. The 12-V gear reduction starter on the composite vehicle is mounted to the flywheel housing.

24.

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

Technician A states that a DPF needs to be replaced when ash reaches full value. Technician B states a regeneration should be performed when DPF ash reaches its full value.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

Soot is oxidized through regeneration, thereby creating ash. Over time, ash can accumulate in the DPF.

When a DPF reaches its full value of ash, the DPF needs to be disassembled and cleaned using a special cleaning process.

25.

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

The aftertreatment fuel injector is activated after the DOC is over what temperature?

  • 550 °F

  • 650 °F

  • 750 °F

  • 850 °F

Correct answer: 550 °F

The aftertreatment injector is commanded by the ECM to inject fuel into the exhaust system once the DOC inlet temperature is over 550 °F. This injector is needed to raise the exhaust temperature. 

The injector receives fuel from a cut-off valve found on the secondary fuel filter outlet.

26.

Technician A states that an air filter should be replaced when it's dirty. Technician B states that an air filter should only be replaced when the restriction indicator shows excessive restriction.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

An air filter that shows acceptable restriction, even if it is dirty, is still serviceable. Air filters should be replaced when the restriction exceeds manufacturer specifications. Restriction is measured by a restriction gauge, or with a restriction indicator installed on the vehicle.

If the restriction indicator isn't reset when serviced, it may give a false reading. The technician must reset the indicator, run the engine at full RPM, and check if the indicator reads the same.

27.

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

Technician A states that both the J1939 data links on public and private networks use a pair of twisted unshielded wires. Technician B states that both the J1939 data links on public and private networks use a pair of twisted shielded wires.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

Both the public and private networks use a pair of twisted unshielded wires for the J1939 data link that the modules communicate over. The modules of the private and public link communicate when the key is turned ON.

The public bus uses a 9-pin data link connector in the cab, while the private bus contains a 3-pin data link connector in the engine compartment.

28.

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

With the accelerator at 100% apply, what should APP 2 sensor read on a scan tool?

  • 3.50 volts

  • 1.50 volts

  • 2.50 volts

  • 2.90 volts

Correct answer: 3.50 volts

APP 2 sensor voltage varies between 0.5 and 3.50 volts: 0.5 volts at 0% applied and 3.50 volts at 100% applied.

APP 1 sensor voltage varies between 1.50 and 4.50 volts: 1.50 volts at 0% applied and 4.50 volts at 100% applied.

29.

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

Technician A states that the intake manifold temperature sensor is located before the EGR mixing chamber in the intake manifold. Technician B states that the intake manifold temperature sensor is located after the EGR mixing chamber in the intake manifold.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The intake manifold temperature sensor is used to measure intake manifold temperature. It is located on the intake after the EGR mixing chamber, making technician B correct.

This four-wire solid-state sensor is also referred to as the IMT.

30.

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

What is the pressure range of the intake manifold pressure sensor with full load at rated RPM?

  • 40-45 PSI

  • 45-50 PSI

  • 30-35 PSI

  • 50-55 PSI

Correct answer: 40-45 PSI

Intake manifold pressure sensor with full load at rated RPM is 40 to 45 PSI. The ECM uses the intake manifold pressure sensor to control the turbocharger, injection timing, and fuel metering.

The voltage of the intake manifold pressure sensor reads 0.50 volts with 0 PSI or inHg. The maximum voltage measured is 4.50 volts.

31.

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

Technician A states that a buzzer sounds when the check engine light comes on to alert the driver that there is an issue. Technician B states that the ECM always reduces engine power 30 seconds after the lamp illuminates.

Who is correct?

  • Neither A nor B

  • Technician A

  • Both A and B

  • Technician B

Correct answer: Neither A nor B

When the check engine light (CEL) comes on, it could simply be due to a warning. At this point, the buzzer will not sound and the engine power won't derate, making both technicians incorrect.

If conditions warrant, the engine may enter derate mode, where power is reduced. There's also a shutdown mode to prevent further engine damage from occurring.

32.

Technician A states that fuel pressure should be measured at idle. Technician B states that fuel pressure should be measured at full rated speed.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Fuel pressure should always be measured at idle and full rated speed to determine if there's a problem. High fuel pressure can be just as serious as low fuel pressure.

Fuel filters and fuel pumps work together to supply clean fuel to the engine. If either were faulty, low pressure or volume can occur. High fuel pressure can cause the fuel pump pressure relief to open, leading to low volume.

33.

Technician A states that the voltmeter function of the DMM should be used to check the amperage. Technician B states that the ohmmeter function of the DMM should be used to measure amperage.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

The ammeter function of the DMM is used to check for amperage. Make sure to set the amperage scale to the correct setting before testing. If the wrong scale is set, the fuse in the meter will be damaged.

The voltmeter function measures the voltage, while the ohmmeter checks resistance and for continuity.

34.

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

Technician A states that the fuel pump relay has three modes of operation. Technician B states that the fuel pump relay has four modes of operation.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

The fuel pump relay contains two modes of operation. It's either ON or OFF, making both technicians incorrect.

The main purpose of the fuel pump relay is to supply power to the pump, so fuel can reach the combustion chamber.

35.

A technician is using a pyrometer to find a misfire. Which of the following would lead the technician to a cylinder misfire?

  • One exhaust manifold runner is cooler than the rest

  • One exhaust manifold runner hotter than the rest

  • Low catalytic converter temperature

  • One intake runner is cooler than the rest

Correct answer: One exhaust manifold runner is cooler than the rest

Heat is a by-product from combustion. The cylinder misfiring will show lower temperature readings on the exhaust manifold runner than the other cylinders.

The pyrometer helps to find the misfiring cylinder when measuring during the first few minutes of engine operation.

36.

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

Technician A states that if one of the APP sensors fail, the vehicle will only set a DTC. Technician B states that if a correlation error occurs, the vehicle will set a DTC and only idle.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

When one APP sensor fails, a DTC is set. The engine continues to run normally because the potentiometers are redundant.

If there is an issue with both circuits or sensors, the vehicle will only idle as a safety measure. It will also set a DTC.

37.

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

Technician A states that the NOx sensors display data in PPM. Technician B states that the NOx sensors display data in PSI.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The NOx sensors display data in parts per million (PPM). For this composite vehicle, the NOx IN sensor module has a value range of 0 to 3000 PPM.

The NOx OUT sensor module also contains a value range of 0 to 3000 PPM.

38.

Technician A states that a manometer can be filled with water. Technician B states that a manometer can be filled with mercury.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

A manometer tube is filled with either water or mercury. It's used to measure pressure, and sometimes vacuum.

Water manometers are helpful to technicians because they allow for more precise measurements when working with small values.

39.

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

At what ambient temperature is the DEF heater commanded on?

  • Below 50 °F

  • Below 40 °F

  • Below 30 °F

  • Below 10 °F

Correct answer: Below 50 °F

At temperatures below 50 °F, the ECM energizes the DEF heater relay. At this time, coil resistance is 90 ± 4 Ω. The relay then sends battery voltage (B+) to the DEF system heaters.

40.

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

Technician A states that the electric fuel primer pump is located in line with the fuel pressure line. Technician B states that the electric fuel primer pump is located in line with the fuel suction line.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The electric fuel primer pump is a two-wire pump located in line with the fuel suction line, so technician B is correct. This pump is energized by the electric fuel primer relay.

When the key is ON or the engine is cranking, the pump operates for up to 60 seconds until a valid engine RPM signal is received. At that point, the mechanical lift pump takes over.