P0C8F
Hybrid/EV Battery Temperature Sensor J Circuit Low.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- C
- AreaHybrid propulsion
- 8F
- FaultThe specific fault in that area
What it means
P0C8F means the hybrid or EV battery control unit has detected a low voltage signal from Temperature Sensor J in the traction battery pack. The signal is lower than the expected range, which usually points to a short to ground or a failed sensor. Which part of the pack sensor J monitors depends on the vehicle, so check the manufacturer data.
Symptoms
- Hybrid or EV system warning light on the dashboard
- Reduced power or limited acceleration (limp mode)
- Reduced electric-only driving or lower regenerative braking
- Cooling fan for the battery running constantly or at high speed
- Reduced charging rate or charging refused
- Poor fuel economy on a hybrid because the battery is used less
Possible causes
- Faulty battery temperature sensor J (internal short or failed thermistor)likely
- Sensor signal wire shorted to ground or to another low-voltage circuit, for example from chafing or damagelikely
- Damaged, corroded or water-affected connector or terminals at the sensor or battery modulepossible
- Damaged or faulty sensor harness inside the battery pack, for example after an impact or previous repairpossible
- Fault in the battery control unit or monitoring module input circuitrare
- Outdated control unit software where the manufacturer has issued a fix for this coderare
How to diagnose
- Read all stored and pending codes and the freeze frame data, and note any other battery temperature sensor codes, which may point to a shared wiring or module fault.
- Check the manufacturer data to find where sensor J is located on your model and which circuit it uses.
- Compare the live data for sensor J with the other pack temperature sensors on a cold car; a reading that is far too low or stuck compared with the others suggests a sensor or circuit fault.
- Visually inspect the accessible wiring and connectors for chafing, water ingress, corrosion or damage, and check for signs of a previous repair or impact.
- Only after following the manufacturer's high-voltage isolation and safety procedure, and only if you are trained to do so, measure the sensor resistance and the circuit for a short to ground against the specification.
- Check the sensor reference voltage and signal circuit continuity between the sensor and the control unit, again within the manufacturer's procedure.
- Check for software updates or technical bulletins relating to this code for the vehicle.
How to fix
- Replace the faulty temperature sensor J or the sensor harness section, following the manufacturer's procedure.
- Repair or replace the shorted or damaged wiring and fix the cause of the damage, such as chafing or a loose mounting.
- Clean or replace corroded or damaged connectors and terminals, and ensure that seals are fitted correctly.
- Replace the faulty battery monitoring module or control unit if the circuit and sensor test good, and then carry out any required coding or setup.
- Update the control unit software if a known fault has been confirmed, then clear the code and retest.
Can I keep driving?
The car can often be driven for a short time, but power may be limited and the battery may not be properly protected from overheating. Have it checked soon, and stop driving if the car shows overheating or serious battery warnings. Hybrid and EV battery work should be done only by trained technicians because of the high-voltage risk.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.