What it means
The HV battery temperature sensor H reports a circuit intermittent/erratic fault. Cell-group temperature monitoring impaired on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Temperature sensor H supplies the battery management system with a reading for its assigned HV battery cell group. P0C85 sets when the sensor H circuit signal becomes unstable or erratic, often because its connector or ground reference loses contact intermittently.
Common causes
Most likely first.
- Connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
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 watch sensor H live data for sudden spikes, dropouts, or changes that do not match nearby sensors.
- Inspect sensor H's connector for incomplete seating, corrosion, loose pins, or signs that vibration could interrupt contact.
- Inspect the sensor H wiring and ground reference for chafing, looseness, or damage, following the manufacturer's high-voltage safety procedure.
- If permitted by the manufacturer's diagnostic procedure, monitor sensor H data while gently checking the accessible low-voltage connector and harness for an intermittent change.
- Test the sensor H circuit's connections and ground reference for intermittent continuity or contact faults using the manufacturer's procedure.
Common fixes
- Reseat and secure the sensor H connector.
- Clean or repair loose or corroded connector pins.
- Repair damaged wiring or a poor ground reference in the sensor H circuit.
- Replace sensor H if the intermittent fault remains and the sensor fails the specified test.
Can I keep driving?
If the warning is on or the vehicle has reduced power, avoid charging and strenuous driving until the intermittent sensor H signal is diagnosed. A signal dropout can prompt battery protection limits, and worsening power loss is a reason to stop safely.
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.