What it means
The signals of the HV battery temperature sensors G and H do not correlate within the calibrated tolerance.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
HV battery temperature sensors G and H report temperatures from their respective cell-group locations, and the battery management system checks that the readings correlate. P0C87 sets when the G-to-H difference exceeds the allowed tolerance, pointing to a possible fault in either sensor or its circuit.
Common causes
Most likely first.
- Faulty battery temperature sensor G or H
- Damaged wiring or poor connection in a sensor circuit
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
- Use a hybrid-capable scan tool to save freeze-frame data and compare sensors G and H with each other and with nearby battery temperatures.
- Observe whether the G-to-H difference is steady and implausible, changes abruptly, or follows expected changes during charging or operation.
- With the high-voltage system made safe according to the manufacturer's procedure, inspect both sensor G and sensor H connectors and wiring for damage, corrosion, and loose contacts.
- Test both sensor circuits and compare each reading's response with the manufacturer's specifications to determine whether G or H is inaccurate.
- If both sensor readings and circuits pass, check for an abnormal battery-pack temperature pattern or cell-group condition using the applicable manufacturer procedure.
Common fixes
- Secure or clean a poor connection in the sensor G or H circuit.
- Repair damaged wiring to sensor G or sensor H.
- Replace the sensor that fails the manufacturer's response test.
- Repair any confirmed pack condition that is causing an abnormal G-to-H temperature difference.
Can I keep driving?
Avoid charging or hard driving if the hybrid warning or reduced-power mode is active, since the battery controller may restrict operation when sensors G and H disagree. Stop if a battery-temperature warning appears or the vehicle loses substantial power.
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.