EVT Diagnostics & Repair Procedures 5

Question 1

Which CAN bus identifier range is typically reserved for HV powertrain communication in an EV architecture?

Accepted Answer

A dedicated powertrain or HV CAN bus isolated from lower-priority body networks

Answer

HV powertrain components communicate on a dedicated high-speed CAN bus, separated from body and convenience networks to ensure message priority and integrity.

Question 2

A technician is performing a high-voltage system leak test after replacing a coolant fitting on the battery thermal circuit. What fluid property makes a HV coolant leak especially hazardous?

Accepted Answer

Electrical conductivity if contaminated — the coolant used must be non-conductive (dielectric)

Answer

EV battery coolant must be non-conductive (dielectric); a contaminated or wrong coolant can become conductive and create a shock hazard or short circuit within the battery pack.

Question 3

During EV motor stator winding resistance testing, a technician finds one phase reading 0.0 Ω while the others read 0.3 Ω each. What does this indicate?

Accepted Answer

A shorted winding on the phase reading 0.0 Ω

Answer

A reading of 0.0 Ω on one phase while others show normal resistance indicates a shorted winding, which would cause excessive current draw and motor damage.

Question 4

When an EV is towed after a collision, what towing method should be used if the drive wheels cannot be lifted?

Accepted Answer

Flat-bed towing only, or use a dolly under the drive wheels

Answer

Rolling drive wheels spin the motor and can generate back-EMF into the inverter or charge the HV battery unexpectedly; a flatbed or dolly eliminates this risk.

Question 5

A scan tool live data PID shows motor inverter temperature at 105°C during a performance test. The vehicle enters 'limp mode.' What is the CORRECT diagnosis?

Accepted Answer

Inverter overtemperature protection has activated — the thermal management system or cooling circuit should be inspected

Answer

Most inverters derate or enter limp mode at high temperatures to prevent IGBT damage; the cooling circuit (pump, coolant level, heat exchanger) must be inspected.

(EVT) Certified Electric Vehicle Technician Practice Test

(EVT) Certified Electric Vehicle Technician Practice Test

EVT Diagnostics & Repair Procedures 5