EVT Diagnostics & Repair Procedures 2

Question 1

When diagnosing an EV that shows a high-voltage interlock loop (HVIL) fault, what is the FIRST step a technician should take?

Accepted Answer

Verify all HV connectors are fully seated and service plugs are installed

Answer

An HVIL fault typically indicates an open circuit in the interlock loop, often caused by an unseated HV connector or removed service plug.

Question 2

An EV's onboard charger (OBC) is not accepting AC power. After confirming the EVSE output is correct, what should the technician check next?

Accepted Answer

AC inlet pilot signal and proximity detection circuits

Answer

The pilot signal and proximity detection circuits between the EVSE and OBC must be within spec for the OBC to enable charging.

Question 3

A technician measures isolation resistance on an EV HV system and gets 150 kΩ. What does this indicate?

Accepted Answer

A serious isolation fault requiring immediate HV system inspection

Answer

Acceptable HV isolation resistance is typically above 500 kΩ (often 1 MΩ+), so 150 kΩ indicates a serious isolation fault requiring inspection.

Question 4

Which tool is used to confirm HV bus capacitors are fully discharged before working on an EV drive system?

Accepted Answer

Calibrated high-voltage rated digital multimeter

Answer

A calibrated high-voltage rated DMM is required to verify that HV bus voltage has dropped to a safe level (typically below 60V DC).

Question 5

An EV shows reduced regenerative braking performance. Which component failure is MOST likely responsible?

Accepted Answer

Degraded HV battery state-of-charge acceptance (high SOC)

Answer

Regen braking requires the HV battery to accept charge; if the battery is near full SOC or has degraded acceptance, regen performance is reduced.

(EVT) Certified Electric Vehicle Technician Practice Test