P0C98

What it means

P0C98 means the hybrid or electric vehicle battery management system has found that one of the battery temperature sensors, identified as sensor L, is giving a reading that is implausible or does not behave as expected. The control unit compares the sensor's value with the other pack temperature sensors, with ambient temperature after a cold soak, or with how the temperature should change under load. Which sensor 'L' is, and where it sits in the pack, depends on the model.

Symptoms

• Hybrid or EV system warning light, or a general warning light on the dashboard
• Reduced power or limited electric assist or charging
• Battery cooling fan running louder or more often than normal
• Reduced electric-only range or charging rate
• Car going into a limp or protection mode
• Fault logged with no obvious change in how the car drives

Possible causes

• Faulty or drifting battery temperature sensor (thermistor)likely
• Damaged wiring, poor connection or corroded terminals in the sensor circuitlikely
• Real temperature imbalance in the pack caused by a cooling fault, such as a blocked air intake or duct, a failed fan, or a coolant circuit problem depending on the modelpossible
• Fault in the battery monitoring or management unit that reads the sensorpossible
• Moisture or contamination in the battery pack connectors or sensor harnesspossible
• Internal pack or module fault causing a genuine local hot or cold spotrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting pack temperatures, ambient temperature, load and state of charge when the fault set.
2. Check for other battery, cooling fan or temperature sensor codes, which can point to a cooling fault rather than a sensor fault.
3. Compare the live reading of sensor L with the other pack temperature sensors, especially after the car has been left to cool for several hours, when they should all be close to ambient.
4. Check the battery cooling system: air intake and filter, ducting, fan operation, or the coolant level and circulation if the pack is liquid cooled. Follow the model's procedure.
5. Have a trained high-voltage technician isolate the system following the manufacturer's procedure, then inspect the sensor wiring and connectors for damage, corrosion, moisture or pushed-out pins.
6. Test the sensor circuit resistance and the signal and reference voltages against the manufacturer's specification, and check for shorts or open circuits in the wiring.
7. Check the manufacturer's technical information for known faults on this model, as the sensor location and replacement method vary.
8. If the sensor and wiring test good, test the battery monitoring unit and look for a real temperature imbalance inside the pack.

How to fix

• Replace the faulty temperature sensor, or the sensor harness or module it is part of, as the manufacturer specifies.
• Repair or replace damaged wiring and clean or replace corroded or loose connectors.
• Restore proper battery cooling by cleaning or clearing blocked air paths, or by repairing the fan or coolant circuit.
• Dry out and seal any moisture-affected connectors, and fix the source of the water ingress.
• Replace or repair the battery monitoring unit if testing shows it is misreading a good sensor.
• Repair or replace the affected battery module only if a genuine internal fault is confirmed, using a trained high-voltage technician.

Can I keep driving?

Nearby codes

• P0C97GenericHybrid/EV Battery Temperature Sensor L Circuit
• P0C99GenericHybrid/EV Battery Temperature Sensor L Circuit Low