310T Electrical and Electronic Systems 3

Question 1

A truck's ABS warning lamp stays on after the vehicle exceeds 6 mph. What is the MOST likely cause?

Accepted Answer

Faulty wheel speed sensor or damaged tone ring

Answer

The ABS ECU monitors wheel speed sensors continuously; a faulty sensor or damaged tone ring will prevent the self-test from clearing and keep the warning lamp illuminated.

Question 2

When testing a truck's charging system, the technician measures 13.2 V at the battery with the engine running at 2,000 RPM and all accessories on. What does this indicate?

Accepted Answer

Undercharging — alternator output is insufficient

Answer

A fully loaded charging system should maintain 13.8–14.5 V; 13.2 V indicates the alternator is not keeping up with electrical demand.

Question 3

A technician finds excessive resistance in a truck's starting circuit. Which tool is BEST suited to locate the high-resistance connection?

Accepted Answer

Voltmeter performing a voltage-drop test

Answer

A voltage-drop test with the circuit under load reveals resistance losses across connections without needing to break the circuit.

Question 4

On a multiplex (J1939 CAN bus) system, a technician notices multiple modules going offline intermittently. The MOST likely cause is:

Accepted Answer

An open or shorted CAN bus terminating resistor

Answer

The CAN bus requires two 120-ohm terminating resistors (240 ohms in parallel = 60 ohms) for proper signal integrity; a missing or shorted resistor causes bus-wide communication failures.

Question 5

A coach's air conditioning compressor clutch engages but immediately disengages. Which electrical component should the technician check FIRST?

Accepted Answer

High-pressure and low-pressure refrigerant switches

Answer

Pressure switches open the compressor clutch circuit when refrigerant pressure is out of range, causing rapid engage/disengage cycling.

(310t) Truck and Coach Technician Certification Practice Test

(310t) Truck and Coach Technician Certification Practice Test

310T Electrical and Electronic Systems 3