P0C88

What it means

P0C88 means the hybrid or EV battery control unit has detected a fault in the circuit of battery temperature sensor 'I'. The unit saw a signal from that sensor that was out of the expected range, implausible, or missing, such as a very high or low voltage or a reading that does not match the other pack sensors. Which part of the pack sensor 'I' monitors depends on the model, so check the manufacturer's data for the vehicle.

Symptoms

• Hybrid system or battery warning light on the dashboard
• Reduced power or limited acceleration
• Reduced regenerative braking or battery charging and discharging
• Battery cooling fan running constantly or at high speed
• Reduced electric-only driving or the engine running more often than usual
• Reduced EV range or a fault when charging

Possible causes

• Faulty battery temperature sensor 'I' (open or short circuit inside the sensor)likely
• Damaged, chafed or corroded wiring between the sensor and the battery control unitlikely
• Loose, corroded or poorly seated connector at the sensor or the control unitlikely
• Sensor reference supply or ground fault affecting the circuitpossible
• Blocked or restricted battery cooling airflow or coolant fault causing a genuine temperature mismatch that is flagged as a circuit or plausibility problempossible
• Fault inside the battery management or control unitrare
• Moisture or damage inside the battery pack affecting the sensor harnessrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting battery temperatures, state of charge and vehicle speed when the fault set, and look for related battery or cooling codes.
2. Check for manufacturer technical bulletins and known issues for this model and battery type.
3. Compare the live data for all battery temperature sensors with the car cold. They should all be close to ambient. Note whether sensor 'I' reads an extreme, fixed or erratic value.
4. Visually inspect accessible wiring and connectors for damage, corrosion, water ingress or loose pins. Only work on the high-voltage system if you are trained and have followed the correct isolation procedure.
5. Check the battery cooling system: air intake, filter and ducts, fan operation, or coolant level and flow, depending on the model.
6. With the system isolated, test the sensor circuit for continuity, short to ground or supply, and resistance against the manufacturer's specification for the sensor.
7. Check the supply and ground to the sensor circuit at the control unit connector.
8. Clear the code after repair and road test, rechecking live temperature data to confirm the fault does not return.

How to fix

• Repair or replace damaged wiring, and clean or refit connectors, so the circuit is sound.
• Replace the faulty temperature sensor or the sensor harness. On some models this is part of a pack module, so follow the manufacturer's procedure.
• Clear blockages in the battery cooling ducts or replace the filter, and repair any fan or coolant circuit faults found.
• Repair any supply or ground fault on the sensor circuit.
• Replace or reprogram the battery control unit only if testing proves it faulty, or if an updated calibration is a known fix for this fault on the model.

Can I keep driving?

Nearby codes

• P0C87GenericHybrid/EV Battery Temperature Sensor G/H Correlation
• P0C89GenericHybrid/EV Battery Temperature Sensor I Range/Performance