×

Quiz Session - Attempts With Random Questions

ASE L1 Exam Questions

Page 8 of 10

141.

What is the dormant voltage of CAN High (H)?

  • 0.25 volts

  • 0.65 volts

  • 4.65 volts

  • 11 volts

Correct answer: 0.25 volts

Dormant CAN H has a voltage of 0.25 that rises to 0.65 volts when communication is occurring. 

Dormant CAN Low (L) has a dormant voltage reading of 11 that drops to 4.65 volts when it's active. 

142.

Enhanced emissions tests are being discussed. Technician A says the EVAP system may be checked for leaks by pressurizing the system to 0.5 psi. Technician B says a vehicle will pass as long as the pressure remains above 8 inches of water during the test period. 

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. In some locations, enhanced emissions tests include a check of the vehicle's evaporative emissions (EVAP) system. To test the system, it is pressurized to 0.5 psi with nitrogen. Then, the equipment measures the rate of pressure drop. A vehicle will pass as long as the pressure remains above 8 inches of water during the two-minute test period. 

143.

Ignition coil secondary resistance should measure in which of the following ranges on the composite vehicle?

  • 8-12K Ω

  • 0.5-1.5K Ω

  • 4-6K Ω

  • 2-3K Ω

Correct answer: 8-12K Ω

Ignition coil secondary resistance for the composite vehicle should be 10K +/- 2K ohms, which would be between 8 and 12K Ω. 

The coil primary resistance is much lower, measuring 1 ± 0.5 Ω, or 0.5 to 1.5 Ω.

144.

Which type of sensor works in conjunction with a toothed wheel (reluctor wheel)?

  • Permanent magnet (PM) sensor

  • Hall effect sensor

  • Proximity sensor

  • Photo-optical sensor

Correct answer: Permanent magnet (PM) sensor

A PM sensor works in conjunction with a toothed wheel called a reluctor. The sensor produces AC signals that can be used by the ECM to calculate engine rpm. 

145.

Alcohol concentration above what percentage will cause a vehicle to run lean?

  • Above 10%

  • Above 5%

  • Above 2%

  • Above 15%

Correct answer: Above 10%

If an alcohol concentration exceeds about 10% by volume, it can cause the engine to run lean. Excessive alcohol content can also damage the fuel pump. 

146.

Which of the following makes up 78% of the air we breathe?

  • Nitrogen 

  • Oxygen 

  • Carbon dioxide 

  • Methane

Correct answer: Nitrogen 

The air we breathe is made up of 78% nitrogen, 21% oxygen, and 1% other gases. 

147.

Technician A says a stuck open PCV valve will cause a rough idle. Technician B says a stuck open PCV valve will cause stalling.

Who is correct? 

  • Neither A nor B

  • Technician A

  • Technician B

  • Both A and B

Correct answer: Neither A nor B 

Neither technician is correct. The PCV valve being stuck closed will cause rough idle/stalling. When it is stuck open, the result is oil siphoning. 

148.

While using a gas analyzer on a vehicle equipped with an electric secondary air injection pump, it is noted that O2 levels are high upon start-up and under wide open throttle (open loop). Technician A says there must be a vacuum leak somewhere. Technician B says this could be a normal vehicle operation. 

Who is correct?

  • Technician B

  • Technician A

  • Neither A nor B

  • Both A and B

Correct answer: Technician B

Only technician B is correct. High oxygen (O2) readings upon start-up and at wide open throttle (open loop) are normal for a vehicle equipped with an electric secondary air injection pump since the pump is operated during these times. 

149.

What should the manifold absolute pressure (MAP) reading be under Key On, Engine Off (KOEO) conditions?

  • 29.5 in. Hg

  • 11.5 in. Hg

  • 22.5 in. Hg

  • 18.5 in. Hg

Correct answer: 29.5 in. Hg

Under KOEO conditions, the MAP value should be close to 29.5 in. Hg. This reading is the equivalent of sea level atmospheric pressure. 

When the engine is idling, the reading should drop to 11.5 in. Hg. This value measures the pressure inside the intake manifold. 

150.

What do positive fuel trim values indicate?

  • Lean air-fuel ratio

  • Rich air-fuel ratio

  • Balanced air-fuel ratio

  • Malfunctioning ECM

Correct answer: Lean air-fuel ratio

The ECM's goal is to keep the air/fuel mixture as close to 14.7:1 as possible. It does so by monitoring the O2 sensors and adjusting fuel delivery accordingly. 

If the fuel trim values are positive, the ECM is adding more fuel to compensate for a lean air-fuel ratio. Negative values indicate the opposite, a rich air-fuel ratio. 

151.

Technician A says multi-port fuel injection (MFI) systems are a "wet manifold" design. Technician B says in a throttle body injection system (TBI), the intake manifold is used exclusively for air induction. 

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. In a multi-port fuel injection (MFI) system, the intake manifold is used exclusively for air induction. TBIs use a "wet manifold" design in which fuel is delivered above the throttle plates and down into the intake manifold. 

152.

All the following are true regarding the ECM of the composite vehicle EXCEPT:

  • Receives power from the alternator

  • Provides a 5-volt supply to most of the engine sensors

  • Contains 120 Ω terminating resistor for the data bus

  • Control features include a vehicle anti-theft immobilizer system

Correct answer: Receives power from the alternator

The ECM of the composite vehicle does not receive power from the alternator. Power comes from the battery and ignition switch. Then, the ECM sends a 5-volt supply of power out to most of the engine sensors.

The ECM does contain a 120 Ω terminating resistor for the data bus and control features, such as the vehicle anti-theft immobilizer system. 

153.

Which of the following is an indicator of combustion efficiency? 

  • CO2

  • CO

  • O2

  • HC

Correct answer: CO2

Carbon dioxide (CO2) levels are an indicator of combustion efficiency. An engine that is running well should generally have CO2 readings that measure between 13% and 17%.

CO2 is a verification gas during state emissions testing. 

154.

The composite vehicle is being discussed. If the vehicle is producing excessive NOx, what could be the EGR position sensor voltage reading?

  • 0.50 volts 

  • 2.50 volts

  • 3.50 volts 

  • 4.50 volts

Correct answer: 0.50 volts 

The EGR valve position sensor output varies between 0.50 volts when the valve is completely closed and 4.50 volts when the valve is completely open. When the EGR valve is stuck closed, combustion temperature increases, as does NOx output. 

A voltage reading of 4.50 indicates that the EGR valve is fully open. 

155.

Technician A says when a faulty module is removed from the network, the other modules can communicate normally. Technician B says if one module fails to send needed information over the network, the other modules will set a communication failure for it. 

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. If one module fails to send needed information over the network, the other modules will set a communication failure for it. To pinpoint the failing module, remove each module one at a time until communication resumes. 

Communication should occur normally once the defective module is removed from the network.

156.

An injector balance test is being performed. The pressure drop for all the injectors is between 15 and 18 psi, except for one cylinder, #3, which measures 5 psi. 

What does this indicate about the #3 injector?

  • It's clogged

  • High resistance

  • Low resistance

  • It's leaking

Correct answer: It's clogged

An injector balance test is used to find mechanical problems with fuel injectors. A lower-than-normal pressure drop reading indicates a clogged injector, while a higher-than-normal pressure drop reading indicates a leaking injector. 

157.

All the following can raise the ignition system voltage required to fire a spark plug EXCEPT:

  • High resistance in the coil primary circuit

  • Excessive resistance in the spark plug wires

  • A lean air/fuel mixture

  • Excessive carbon deposits in the combustion chamber 

Correct answer: Shorted primary windings in the coil

High resistance in the coil primary circuit would lower the available ignition system voltage as opposed to raising the required voltage. 

All the other options would raise the voltage required to fire the spark plugs. 

158.

On the composite vehicle, the heated O2 sensor output varies between which of the following?

  • 0.0 to 1.0 volts

  • 0 to 5 volts

  • 1 to 2 volts

  • 0 to 12 volts

Correct answer: 0.0 to 1.0 volts

O2 output varies from 0.0 - 1.0 volts, depending on the conditions. They are mounted after the front catalytic converters on each bank in the exhaust pipe. These sensors are used for catalytic converter efficiency and OBD monitoring. 

159.

All the following conditions cause the electronic throttle control system on the composite vehicle to be disabled EXCEPT:

  • Faulty idle air control valve (IAC)

  • Failure of both APP sensors

  • Correlation error

  • Failure of both TP sensors

Correct answer: Faulty idle air control valve (IAC)

The composite vehicle doesn't contain an IAC, throttle cable, or cruise control actuator. Instead, it uses input from two accelerator pedal position sensors to determine control of the throttle actuator. 

If both of the sensors or the TP sensors fail, the throttle position will be limited to 15%, and the vehicle will be stuck in limp-in mode. The electronic throttle control system will also be disabled if there's a correlation issue. 

160.

Two technicians are discussing a communications issue with the composite vehicle. Technician A states that a powertrain communications failure prevents the ECM from controlling the ignition system. Technician B states one 120-ohm terminating resistor is located in the ECM, and the other is in the instrument cluster. 

Who is correct? 

  • Technician B

  • Technician A

  • Both technicians

  • Neither technician A nor B

Correct answer: Technician B

Technician A is incorrect. A powertrain communications failure doesn't prevent the ECM from providing control of the vehicle's ignition system.

Technician B is correct. The powertrain communications network contains two 120-ohm terminating resistors. One is found in the ECM, and the other is in the instrument cluster. 

×