Diagnosing EV and Hybrid Concerns
Diagnosing EV and Hybrid Concerns
High voltage systems operate at 200 to 800 volts DC. Contact is potentially lethal. Always follow manufacturer-specific de-energization procedures. Always verify with a CAT III rated meter that the system is completely de-energized before any work near HV components. Never assume — verify.
12V battery — check it first
Every EV and hybrid has a conventional 12-volt battery that powers all accessories and control modules. A dead 12V battery on an EV produces the same symptoms as a dead battery on any conventional vehicle — no power, no communication, will not start. Check the 12V battery before any other diagnosis on an EV accessory or communication concern.
Range reduction complaint
Check battery State of Health from the scan tool before any other diagnosis. All lithium batteries degrade over time. If SOH is at 80 percent, the battery delivers 80 percent of its original range — that is the expected range now, not a fault. If SOH is appropriate for the mileage and age, educate the customer. If SOH has dropped abnormally — investigate the battery management system for cell imbalance or thermal management faults.
Charging faults
Scan all modules — not just the EV control module. Charging involves the onboard charger, the battery management system, the HV battery, and communication between the vehicle and the charging station. A fault in any of these prevents charging. Check for ground fault codes — a HV insulation fault prevents the system from operating as a safety measure. Manufacturer-specific diagnostic procedures are essential for EV diagnosis.