I-CAR - Inter-Industry Conference on Auto Collision Repair Certified Vehicle Electrical Diagnostics Questions and Answers

Question 1

A technician is performing a parasitic draw test on a modern vehicle.
After connecting a DVOM in series with the negative battery cable, the initial reading is 2.5 amps.
After 45 minutes, the reading stabilizes at 85 milliamps (0.085A).
What is the MOST likely cause for this reading?

Accepted Answer

One or more control modules have failed to enter 'sleep mode'.

Answer

A faulty alternator diode is allowing a constant current draw.

Answer

This is a normal reading as vehicle modules have entered 'sleep mode'.

Answer

The battery has a shorted internal cell causing a continuous discharge.

Question 2

When performing a voltage drop test on the ground side of a starter motor circuit, a technician connects the red lead of a DVOM to the starter motor housing and the black lead to the negative battery terminal. While cranking the engine, the meter reads 0.9 volts. What does this reading indicate?

Accepted Answer

There is excessive resistance in the ground circuit between the starter and the battery.

Answer

The starter motor has excessive internal resistance.

Answer

The battery is undercharged and cannot supply enough voltage.

Answer

The positive-side starter cable has a poor connection at the solenoid.

Question 3

A technician is diagnosing a communication issue on a high-speed CAN bus network. Using a multimeter with the battery disconnected, what should the resistance be when measuring between the CAN High (Pin 6) and CAN Low (Pin 14) terminals at the DLC?

Accepted Answer

Approximately 60 ohms.

Answer

Approximately 120 ohms.

Answer

Infinite resistance (OL).

Answer

Zero ohms (continuity).

Question 4

Which of the following measurements requires the Digital Volt-Ohm Meter (DVOM) to be connected in series with the circuit being tested?

Accepted Answer

Amperage (Current)

Answer

Voltage

Answer

Resistance

Answer

Voltage Drop

Question 5

A vehicle comes in with an inoperative right front headlight (low beam). The technician has confirmed the bulb and fuse are good. The next step is to check for power at the headlight connector. With the headlight switch on, the technician measures the voltage between the power wire at the connector and a known good chassis ground. The DVOM reads 12.4 volts. What is the most likely cause of the problem?

Accepted Answer

A faulty or missing ground connection for the headlight bulb.

Answer

A short-to-ground in the power feed wire.

Answer

An open circuit in the power feed wire.

Answer

High resistance in the headlight switch.

Question 6

When using a DVOM to test for an open circuit (infinite resistance) in a section of wire, what is the proper procedure?

Accepted Answer

Isolate the wire from the circuit, set the DVOM to Ohms (Ω), and connect the leads to each end of the wire.

Answer

Connect the leads to both ends of the wire with the circuit energized and check for voltage.

Answer

Connect the leads in series with the wire and check for amperage while the circuit is active.

Answer

Connect the leads across the component's power and ground wires with the circuit energized.