Deck 15: Modern Truck Electrical System

Question 1

Referring to the following figure, a short to ground of the CAN + circuit at the engine ECM stub would cause all CAN communications between modules to not be possible.

Answer 1

True

Question 2

Referring to the figure shown below, a missing terminating resistor would cause the resistance between the CAN + and CAN - pins of the 9-pin diagnostic connector with the batteries disconnected to be approximately 120 ohms.

Answer 2

True

Question 3

Referring to the figure shown below, an open CAN - circuit between the instrument cluster and the transmission ECU would cause the resistance between the CAN + and CAN - pins of the 9-pin diagnostic connector with the batteries disconnected to be approximately 120 ohms.

Answer 3

True

Question 4

A four-channel ABS system would only be used on a vehicle with four wheels.

Question 5

The ABS ECU determines that wheel lockup is about to occur based on the frequency generated by the wheel-speed sensors.

Question 6

In a series hybrid system, the vehicle is propelled only by electric motor(s).

Question 7

The battery power fuse for an Allision WTEC ECU (TCM) is blown. What would be the most likely indication of this problem?

A) Engine will not crank
B) Transmission will only shift into third range and reverse.
C) Allision WTEC ECU would set a DTC indicating the battery power fuse is blown.
D) Shift points are not correct.

Question 8

Referring to the figure shown below, Technician A says that an open CAN + circuit between the engine ECM and the body ECU could cause the automatic transmission shift points to be affected. Technician B says that an open CAN + circuit in the ABS ECU stub could cause the ABS warning lamp to be illuminated in the instrument cluster. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 9

Which of the following sensors would be found on an Eaton AutoShift AMT?

A) Torque speed control (TSC) sensor
B) Turbine speed sensor
C) Yaw rate sensor
D) Rail select position sensor

Question 10

Technician A says that a two-pedal automated manual transmission (AMT) does not require any type of clutch between the engine and transmission. Technician B says that an electronic clutch actuator (ECA) would be used with a three-pedal AMT. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 11

Technician A says that a blown air ABS ECU battery power fuse will prevent the service brakes from operating. Technician B says that a chuff test is performed to test wheel speed sensors. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 12

The ABS warning lamp is illuminated continuously. What could cause this?

A) Open wheel speed sensor circuit
B) ABS fail-safe relay has been removed
C) Open CAN+ circuit
D) All of the above could cause the ABS warning lamp to illuminate depending upon the type of system.

Question 13

Technician A says that too large of an ABS wheel speed sensor air gap will result in a large increase in the sensor resistance which can be detected with a DMM ohmmeter. Technician B says that a DMM voltmeter should be set to the DC volts setting when testing an ABS wheel speed sensor. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 14

Which of the following would cause the trailer ABS warning lamp in the tractor to illuminate?

A) A trailer with ABS has just been connected to the tractor
B) A trailer with ABS has just been disconnected from the tractor
C) The trailer ABS ECU has detected an open wheel speed sensor circuit.
D) All of the above could cause the trailer ABS warning lamp to illuminate.

Question 15

Technician A says that depressing the brake pedal on a truck with Meritor-Wabco Hydraulic Power Brake (HPB) that has completely discharged accumulators would still cause the brake calipers to apply the brakes but with reduced force. Technician B says that completely discharged accumulators would prevent the SAHR park brake from applying. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 16

Which of the following is a true statement?

A) Disconnecting the vehicle speed sensor will always prevent an EOBR from detecting that the vehicle is in motion.
B) Each truck operator has his own EOBR; if the operator changes trucks the EOBR is removed and stays with the operator.
C) An EOBR can be considered as an electronic log book.
D) All of the above are true statements.

Question 17

Technician A says that automatic traction control can involve the ABS ECU transmitting a torque speed control J1939 message. Technician B says that automatic traction control (differential braking) can involve application of the service brake on the wheel that is spinning. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B

Question 18

A work order indicates that the ABS warning lamp is illuminated. Which of these would be the first step of the troubleshooting process?

A) Check for pushed out wheel speed sensors.
B) Perform a chuff test.
C) Use a DMM voltmeter to test each wheel speed sensor.
D) Verify the complaint.

Question 19

Which of the following is true for an Eaton hybrid electric system?

A) The Eaton hybrid electric system is a parallel hybrid system.
B) An Eaton UltraShift AMT with electronic clutch actuator (ECA) is used as the transmission.
C) The inverter converts 340V DC into a variable-frequency three-phase AC voltage.
D) All of the above are true.

Question 20

A technician is diagnosing a J1939 communication problem. The following measurements were obtained using a DMM voltmeter at the 9-pin diagnostic connector:
CAN + to CAN - 3V
CAN + to ground 2.5V
CAN - to ground 2.5V
What do these readings indicate?

A) CAN + is not shorted to CAN -.
B) CAN + is not shorted to ground.
C) CAN - is not shorted to ground.
D) All of the above.