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Quiz Session - Attempts With Random Questions

ASE L2 Exam Questions

Page 9 of 15

161.

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

Technician A states that the crankcase pressure sensor sends data to the BCM. Technician B states that the crankcase pressure sensor sends data to the ECM.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The crankcase pressure sensor monitors the crankcase pressure and sends the data back to the engine control module (ECM). This data verifies the condition of the closed crankcase ventilation system and filter.

The body control module (BCM) on the composite vehicle is responsible for the cruise control on/off switch, ambient air temperature sensor, engine brake on/off switch, as well as other switches.

162.

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

Technician A states that the DOC/DPF temperature sensor module is part of the exhaust aftertreatment system. Technician B states that the PM sensor module is part of the exhaust aftertreatment system.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Both the DOC/DPF temperature sensor module and the PM sensor module are part of the exhaust aftertreatment system. Other components include:

  • Decomposition reactor tube
  • Diesel oxidation catalyst (DOC)
  • Diesel particulate filter (DPF)
  • Selective catalytic reduction (SCR) unit

This system is further comprised of:

  • Aftertreatment (AFT) air purge
  • Aftertreatment (AFT) fuel injector
  • Aftertreatment (AFT) fuel pressure sensor
  • Aftertreatment (AFT) fuel shutoff
  • Diesel exhaust fluid (DEF)
  • Diesel exhaust fluid (DEF) line heaters
  • Diesel exhaust fluid (DEF) quality/level/temperature sensor module
  • Diesel exhaust fluid (DEF) supply pump
  • Diesel exhaust fluid (DEF) tank
  • Diesel exhaust fluid (DEF) tank heater
  • Diesel particulate filter differential pressure/diesel particulate filter outlet pressure (DPFDP/DPFOP) sensor
  • Doser valve
  • NOx IN sensor module
  • NOx OUT sensor module

163.

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

Technician A states that the charge air cooler outlet temperature sensor is a two-wire sensor. Technician B states that the charge air cooler outlet temperature sensor has one battery voltage circuit and one ground circuit.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The charge air cooler outlet temperature sensor is a two-wire connector, making technician A correct. Technician B is incorrect because the charge air cooler outlet temperature sensor contains one signal wire and one ground wire.

The charge air cooler outlet temperature sensor is connected to the ECM at terminals 361 and 362.

164.

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

Technician A states that the fuel volume control solenoid is mounted to the pump. Technician B states that the fuel volume control solenoid is mounted on the pressurized fuel line.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The fuel volume control solenoid is mounted to the pump, making technician A correct. It works to control the volume of fuel into the high-pressure pumping chambers.

With the key OFF, the solenoid defaults to an open position.

165.

Technician A states that fuel supply system pressure should be checked with the engine loaded. Technician B states that fuel supply system pressure should be checked at idle.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B 

  • Neither A nor B

Correct answer: Technician A

Fuel supply system pressure should be checked with the engine running at a full load. A supply system may be able to supply at idle or with a light load, but unable to when under a load.

To further test, some manufacturers have tools that use a calibrated orifice to replicate an engine that operates under a load.

166.

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

Technician A states that the intake manifold pressure sensor signal is used by the ECM for turbo charger control. Technician B states that the intake manifold pressure sensor signal is used by the ECM to control fuel metering.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

This four-wire sensor measures the intake manifold pressure. The ECM uses the intake manifold pressure sensor signal for both turbo control and fuel metering.

Intake manifold pressure is vital to the engine running properly. Full load at rated RPM measures 40 to 45 PSI (276 to 310 kPa).

167.

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

Technician A states that the aftertreatment air purge valve is located after the AFT fuel injector. Technician B states that primary air tank supplies air to the aftertreatment air purge valve.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

The aftertreatment air purge valve is located before the AFT fuel injector. It is needed to purge fuel from the aftertreatment fuel injector and line.

Air to the aftertreatment air purge valve is supplied from the secondary air tank.

168.

Technician A states that resistors are used to restrict current. Technician B states that resistors with a loss of ground will cause sensor value and reference voltage to be different regardless of the sensor position.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

Resistors are either a two- or three-wire design and are used to restrict current, making technician A correct. A resistor is only a resistor when it is placed under a load.

If there's a loss of the ground connection, the sensor value and reference voltage will be the same, making technician B incorrect. This factor is critical on a diesel engine because the TPS is needed to throttle the motor.

169.

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

Technician A states that the NOx IN sensor module communicates on the J1939 private CAN. Technician B states that the NOx OUT sensor module communicates on the J1939 public CAN.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The NOx IN sensor module communicates with the ECM on the J1939 private CAN. Additionally, the NOx OUT sensor module uses the J1939 private CAN for communication.

Both sensor modules monitor oxides of nitrogen in the exhaust stream ranging between 0-3000 PPM.

170.

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

Technician A states that the displayed data of the fuel rail pressure sensor can read up to 200 PSI. Technician B states that the displayed data of the fuel rail pressure sensor can read up to 40,000 PSI.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The fuel delivery pressure sensor, not the fuel rail pressure sensor, displays data between 0 and 200 PSI and 0 and 5 volts DC, making technician A incorrect. This displayed data reveals how the information would be shown on a scan tool.

The fuel rail pressure sensor can reveal a reading up to 40,000 PSI, making technician B correct.

171.

Technician A states that a diesel fuel system can produce over 30,000 PSI. Technician B states that it's normal to see a burn pattern on the piston when dismantling a diesel engine.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Diesel engines often use a low pressure pump to ensure enough volume is supplied to the high pressure pump. It is common to have pressure in excess of 30,000 PSI on the high side, making technician A correct. The high pressure can cause personal injury.

Because of the excessive pressure, it's normal to see burn patterns from the fuel on the piston when dismantling a diesel engine, making technician B correct. This is an indication that the injector was providing enough fuel.

172.

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

Technician A states that an open at fuse 91 will cause an interruption of communication with the ECM. Technician B states that an open at fuse 91 will cause the EGR valve to be inoperative.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

Fuse 91 feeds the instrument cluster module. No components on the engine control module side would be affected if this fuse were open.

The issue stemming from fuse 91 blowing is that the instrument cluster module won't receive power.

173.

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

Technician A states that the intake manifold pressure/temperature sensor has two signal wires. Technician B states that the intake manifold pressure/temperature sensor is a four-wire sensor.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

The intake manifold pressure/temperature sensor is a four-wire sensor. It is connected to the ECM at terminals 373-376.

The intake manifold pressure/temperature sensor contains two signal wires: a pressure signal and a temperature signal. It also contains a ground and a 5-V reference.

174.

All of the following complaints would be considered mechanical, except:

  • Shorted injector wiring harness

  • Low compression

  • Clogged fuel injectors

  • Faulty exhaust gas recirculation (EGR) cooler

Correct answer: Shorted injector wiring harness

A shorted injector wiring harness is considered an electrical problem. With a short, power cannot flow to the injector. The wiring harness may need to be replaced or repaired, depending on the recommendation of the manufacturer.

Low compression, clogged fuel injectors, and a faulty exhaust gas recirculation (EGR) cooler are all considered mechanical.

175.

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

Technician A states that the ECM uses the fuel rail pressure sensor for injection timing. Technician B states that the ECM uses the fuel rail pressure sensor to maintain fuel rail pressure control.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

The fuel rail pressure sensor is a strain gauge sensor that monitors the rail pressure. The ECM uses this signal to maintain fuel rail pressure control, not for injection timing.

Pressures range between 5,000 and 45,000 PSI, leaving voltage readings between 0.50 and 4.50 volts.

176.

Technician A states that high boost can be caused by a leaking intake passage. Technician B states that low boost can be caused by a defective turbo.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

Low boost can be caused by a defective turbo or a leaking intake passage. As the engine speeds up, the turbo boost should also increase.

Using the turbo boost measured parameter may help to pinpoint the defect. High exhaust temperatures may also be the result of turbocharger problems.

177.

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

Technician A states that the particulate matter sensor measures soot at the outlet of the exhaust aftertreatment system. Technician B states that the particulate matter sensor measures soot at the inlet of the exhaust aftertreatment system.

Who is correct?

  • Technician A 

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The particulate matter sensor is used to measure the soot emissions at the outlet of the exhaust aftertreatment system. This sensor communicates over the J1939 private CAN to the ECM.

The PM sensor module is found after the selective catalytic reduction (SCR) catalyst in the exhaust aftertreatment system.

178.

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

Technician A states that if fuse 61 was open, the DEF tank heater would be inoperative. Technician B states if fuse 61 was open, none of the DEF heaters would work.

Who is correct?

  • Both A and B

  • Technician A 

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Fuse 61 is the DEF heater relay coil voltage supply. If it were open, the four connected heaters would not work.

The DEF pressure line heater, DEF supply line heater, DEF tank heater, and DEF pump heater all rely on both fuse 61 and fuse 62 to run.

179.

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

How many wires does the intake manifold pressure/temperature sensor have?

  • Four

  • Two

  • Three

  • Five

Correct answer: Four

The sensor has four wires. The first wire is a pressure signal, while the second is a temperature signal. It also contains a ground wire and a 5-V reference. These are connected at pins 373-376.

180.

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

Technician A states that the water-in-fuel sensor is located in the bottom of the primary filter separator. Technician B states that the water-in-fuel sensor is located in the top of the secondary fuel filter separator.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

The water-in-fuel sensor is located in the bottom of the primary fuel filter separator. Its main purpose is to measure how much water is in the fuel.

This two-wire sensor allows the ECM to measure resistance across the terminal pairs at the end of the sensor.

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