NAPA - National Automotive Parts Association Certified Mechanic Electrical and Electronic Systems Questions and Answers

Question 1

A technician is diagnosing a no-communication issue on a high-speed CAN bus.
Using a multimeter with the battery disconnected, what is the expected resistance measurement between the CAN High and CAN Low lines?

Accepted Answer

Approximately 60 ohms

Answer

Approximately 120 ohms

Answer

Infinite resistance (OL)

Answer

Zero ohms

Question 2

A customer's vehicle has a dim headlight and the corresponding taillight is completely out. All other lights function normally. Which of the following is the MOST likely cause?

Accepted Answer

A poor ground connection for that lighting circuit

Answer

A faulty alternator

Answer

A blown fuse for that specific circuit

Answer

A failed lighting control module

Question 3

When performing a voltage drop test on the positive side of a starter circuit, a technician connects a voltmeter between the positive battery post and the starter's main power terminal. While cranking the engine, the meter reads 0.8 volts. What does this reading indicate?

Accepted Answer

Excessive resistance in the positive-side starter cable or connections

Answer

A faulty starter motor

Answer

A fully charged battery

Answer

Normal operation for the starting circuit

Question 4

Which of the following is a critical safety precaution a technician MUST take before working on the high-voltage systems of a hybrid or electric vehicle?

Accepted Answer

Disabling the high-voltage system by removing the service disconnect/plug

Answer

Disconnecting the 12-volt auxiliary battery only

Answer

Wearing standard leather work gloves

Answer

Keeping the vehicle key fob within 5 feet of the vehicle

Question 5

A vehicle's check engine light is on, and a scan tool reveals a code for a malfunctioning Mass Airflow (MAF) sensor. To test the sensor's signal, a technician back-probes the signal wire. What should the technician expect to see on a multimeter or scan tool as the engine RPM is increased from idle?

Accepted Answer

A voltage or frequency that increases smoothly as RPM increases

Answer

A steady voltage of 5.0 volts

Answer

A voltage or frequency that decreases as RPM increases

Answer

A voltage that cycles rapidly between 0.1 and 0.9 volts

Question 6

A vehicle's charging system is being tested. With the engine running at 1500 RPM and all accessories off, the voltage at the battery terminals is 14.2 volts. When the headlights, blower motor, and rear defroster are turned on, the voltage drops to 12.5 volts and continues to fall. This MOST likely indicates:

Accepted Answer

A faulty voltage regulator or failing alternator

Answer

A sulfated battery

Answer

High resistance in the battery ground cable

Answer

Normal charging system operation

A technician is diagnosing a no-communication issue on a high-speed CAN bus.Using a multimeter with the battery disconnected, what is the expected resistance measurement between the CAN High and CAN Low lines?

A technician is diagnosing a no-communication issue on a high-speed CAN bus.
Using a multimeter with the battery disconnected, what is the expected resistance measurement between the CAN High and CAN Low lines?