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Quiz Session - Attempts With Random Questions

ASE L2 Exam Questions

Page 8 of 15

141.

Technician A states that high-pressure common rail injectors require adjustment after installation. Technician B states that hydraulic electronic unit injectors require adjustment after installation.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

HPCR and HEUI injectors require no adjustment after installation. Most HPCR systems are solenoid-operated, so they don't require a rocker or camshaft to operate, therefore, there's no need for adjustment after an installation.

The HEUI system also doesn't require adjustment after the installation, but it may be recommended to replace the hold-down bolts.

142.

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

Technician A states that the exhaust back pressure sensor voltage varies between 1 and 5 volts. Technician B states that as exhaust back pressure increases, voltage decreases.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

The back pressure sensor voltage varies between 0.5 and 4.5 volts, making technician A incorrect.

As pressure increases, voltage increases, making technician B incorrect. When the PSI is 0, the voltage measures 0.50 volts, but when the PSI is 200, the voltage measures 4.50 volts.

143.

Technician A states that high counts of inactive codes signifies an issue with the scan tool. Technician B says that a large number of inactive codes reveals loose connections or intermittent conditions.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

Technician B is correct, as the scanner will read both active and inactive codes. Seeing high counts of inactive codes signifies the possibility of loose connections or intermittent conditions.

Inactive codes can't be diagnosed because they are not active, but are not an indication that something is wrong with the scan tool.

144.

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

What is the minimum normal oil pressure for an engine at normal idle?

  • 15 PSI

  • 50 PSI

  • 35 PSI

  • 75 PSI

Correct answer: 15 PSI

The minimum pressure at normal idle is 15 PSI. The pressures vary up to 70 PSI depending on RPM.

The ECM uses this signal to display on the instrument cluster panel gauge and protect the engine.

145.

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

Technician A states that if the particulate matter sensor detects soot bypassing the DPF, it will set a diagnostic trouble code. Technician B states that if the particulate matter sensor detects soot bypassing the DPF, a message will alert the driver.

Who is correct?

  • Technician A

  • Technician B 

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

If the particulate matter sensor detects soot bypassing the DPF, a trouble code will be set, but there is no message that alerts the driver of the soot problem. At the same time, the engine will derate for protection.

Some engine performance DTCs can inhibit regeneration from starting, or abort regeneration that is occurring.

146.

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

The ignition switch contains all of the following positions, except:

  • ACCESSORY

  • OFF

  • ON

  • CRANK

Correct answer: ACCESSORY

The ignition switch is a three-position switch. It contains the following positions: OFF, ON, and CRANK.

The ignition switch in the composite vehicle doesn't have an ACCESSORY position. This switch provides 12 volts of power to the ECM to communicate with other modules and to request starter operation.

147.

Technician A states that a leaking fuel injector can cause blue smoke. Technician B states that a leaking fuel injector can cause a lean condition.

Who is correct?

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B

A leaking fuel injector is a common cause of a rich condition. Rich-running engines cause black smoke from the exhaust.

Lean-running engines are caused by a lack of fuel or too much air entering the combustion chamber.

Blue smoke is the result of oil entering the combustion chamber. It can be caused by a bad turbocharger seal, defective piston rings, or worn valve guides.

148.

Technician A states that diesel engines emit higher HC and CO than gasoline engines. Technician B states that diesel engines emit higher NOx than gasoline engines.

Who is correct?

  • Technician B

  • Technician A

  • Both A and B

  • Neither A nor B

Correct answer: Technician B

Diesel engines have a higher thermal efficiency, which means the NOx is higher, making technician B correct. In diesel engines, the HC and CO emissions are lower, making technician A incorrect.

The catalytic converters adapted to the diesel engine are known as diesel oxidation catalysts (DOCs). These are designed to reduce harmful emissions.

149.

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

Technician A states that the ECM uses the engine coolant temperature sensor for fuel management. Technician B states that the ECM uses the engine coolant temperature sensor for cooling fan operation.

Who is correct?

  • Both A and B

  • Technician A 

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

The ECM uses the engine coolant temperature sensor for multiple controls — two of them are cooling fans and fuel management. It's also used for DPF regeneration.

The engine coolant temperature sensor is attached to the cylinder head close to the coolant thermostats.

150.

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

Where is the camshaft position sensor located?

  • Engine rocker box cover

  • Engine oil pan

  • Engine front cover

  • Rear of the engine block

Correct answer: Engine rocker box cover

The cam sensor detects the position of the camshaft. It is located in the engine rocker box cover.

It sends the information to the ECM so injection timing and fuel control can be determined.

151.

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

What should the voltage on a scan tool read while monitoring the fuel rail pressure sensor if the pressure was 15,000 PSI?

  • 1.5 volts

  • 2.5 volts

  • 3.5 volts

  • 4.5 volts

Correct answer: 1.5 volts

The pressure and voltage on the fuel pressure sensor vary between 5,000-45,000 PSI and 0.5-4.5 volts. As pressure increases, voltage increases.

When the fuel rail pressure sensor reads 15,000 PSI, the corresponding voltage reading would be 1.5 volts.

152.

Technician A states that the ohmmeter function can be used to check a component's resistance. Technician B says that an ohmmeter should never be used on a live circuit.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Components sometimes have a specific value for resistance and can be checked using an ohmmeter. Ohmmeters also check for continuity.

Ohmmeters are self-powered and should never be used on a live circuit or components.

153.

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

Technician A states that the fuel temperature sensor is mounted to the secondary fuel filter housing. Technician B states that the data from the fuel temperature sensor is sent to the ECM.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A or B

Correct answer: Both A and B

Technician A is correct because the fuel temperature sensor is mounted to the secondary fuel filter housing. This sensor is responsible for monitoring the fuel temperatures.

Technician B is also correct because the data from the fuel temperature sensor is sent to the ECM. The ECM uses the data to compensate for any changes in fuel temperature to protect the engine.

154.

Technician A states that intake air pressure sensors should be checked with the key on and the engine off. Technician B states that intake air pressure sensors should be checked with the engine at idle.

Who is correct?

  • Technician A

  • Technician B

  • Both A and B

  • Neither A nor B

Correct answer: Technician A

Pressure sensors should be checked with the key on and the engine off using a scan tool. Sensors should report a reading of 0.0 PSI.

Once the sensor passes this test, the technician can apply a pressure of about 20 PSI with a pressure/vacuum gun and compare the readings on the scan tool.

155.

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

At what fuel temperature does power derate begin?

  • 180 °F

  • 190 °F

  • 200 °F

  • 210 °F

Correct answer: 180 °F

Temperatures in excess of 180 °F cause a 20% power derate. If the temperature continues to remain too high, derated power increases to 40%.

Derated power (limp mode) causes the amber CEL or MIL to illuminate. The ECM begins to reduce engine power starting 30 seconds after the first warning.

156.

Above what temperature does NOx begin to form?

  • 2500 °F

  • 1500 °F

  • 2000 °F

  • 2200 °F

Correct answer: 2500 °F

With temperatures above 2500 °F, NOx begins to form. If combustion temps remain below this value, NOx won't form.

Because of the high combustion temperatures of diesel engine, the application of an EGR system is critical.

157.

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

Technician A states that engine performance trouble codes may inhibit a regeneration from starting. Technician B states that transmission trouble codes may inhibit a regeneration from starting.

Who is correct?

  • Both A and B

  • Technician A

  • Technician B

  • Neither A nor B

Correct answer: Both A and B

Engine or transmission trouble codes may inhibit a regeneration from starting. If a code sets during a regeneration, the regeneration may be aborted.

158.

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

Technician A states that the ECM uses the signal from the fuel delivery pressure sensor to control injection timing. Technician B states that the ECM uses the signal from the fuel delivery pressure sensor 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

The fuel delivery pressure sensor monitors pressure before the high pressure pump, but after the secondary fuel filter. The ECM uses the signal to control injection timing, making Technician A correct. It also controls fuel delivery, making Technician B correct.

159.

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

When checking the fuel injector resistance across the coil terminals, what should the reading be?

  • 1.5-2.5 ohms

  • .5-1.5 ohms

  • 1-2 ohms

  • 2.5-3.5 ohms

Correct answer: 1.5-2.5 ohms

The coil resistance on the fuel injectors is 2 Ω ± 0.5 Ω, between 1.5-2.5 ohms. Anything outside of the specification may mean that the fuel injector should be replaced.

 Fuel injector quantity adjustment (IQA) occurs through injector calibration coding in the ECM.

160.

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

What component monitors the DPF soot load?

  • DPFDP/DPFOP sensor

  • Selective catalytic reduction (SCR) unit

  • NOx IN sensor module

  • Aftertreatment (AFT) fuel pressure sensor

Correct answer: DPFDP/DPFOP sensor

The DPFDP/DPFOP sensor monitors the DPF soot load. The ECM assigns a level to the amount of restriction.

DPF soot loads are measured between level 0 and level 4, with the higher known as an overfull soot load.

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