What it means
The hybrid control module detects an isolation fault between the high-voltage battery and the vehicle chassis. Indicates degraded HV insulation.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid control module monitors electrical isolation between the high-voltage battery system and the vehicle chassis. P2C85 means it has detected an isolation fault on the external side of the battery pack, such as a chafed high-voltage cable or moisture in a connector.
Common causes
Most likely first.
- HV cable insulation chafed against chassis
- Moisture in HV connector
- Pack cell imbalance approaching service threshold
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Read freeze-frame data and hybrid-system isolation status with a compatible scan tool, and note any related high-voltage or charging codes.
- Check the vehicle for visible damage, water intrusion, or recent repairs near external high-voltage cables and connectors without touching or disconnecting them.
- Have a qualified hybrid technician inspect the external high-voltage cable routing and connectors for insulation damage or moisture using the manufacturer's safety procedures.
- Have the external high-voltage insulation resistance measured with the specified equipment and procedure, then compare results with the manufacturer's limits.
- If external circuits pass, have the battery pack's isolation and cell-balance data evaluated to distinguish an external fault from a pack-related issue.
Common fixes
- Dry and reseal a moisture-affected external high-voltage connector if the manufacturer's procedure permits repair.
- Replace a chafed or damaged external high-voltage cable or connector assembly.
- Repair the confirmed pack-related insulation or cell-balance fault using the manufacturer's service procedure.
Can I keep driving?
Do not continue driving if the vehicle shows reduced power, a high-voltage warning, or charging trouble; arrange service and follow the vehicle's warning instructions. High-voltage isolation faults can create an electric-shock hazard, so do not touch or open high-voltage components.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.