P0ACB
Hybrid/EV Battery Temperature Sensor C Circuit Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- A
- AreaHybrid propulsion
- CB
- FaultThe specific fault in that area
What it means
P0ACB is a generic code meaning the hybrid or EV battery control unit has judged the signal from hybrid/EV battery temperature sensor C to be out of its expected range or implausible compared with other data. The sensor is still producing a signal, but it does not agree with the other battery temperature sensors, with the modelled temperature or with conditions such as coolant or ambient temperature after a soak. Which sensor is 'C' and where it sits in the pack depends on the vehicle, so check the manufacturer data.
Symptoms
- Hybrid or EV system warning light or malfunction indicator on
- Reduced power or limited battery charge and discharge
- Battery cooling fan running loudly or constantly
- Reduced electric-only range or the engine running more than normal
- Reduced or no regenerative braking
- Car going into limp mode in some cases
Possible causes
- Faulty battery temperature sensor C (drifting or reading incorrectly)likely
- Damaged wiring, corrosion or poor connection in the sensor circuit or pack connectorlikely
- Poor sensor contact or a displaced sensor within the battery pack or modulepossible
- Battery cooling problem causing a real temperature imbalance, such as a blocked intake duct, failed fan or coolant fault (depends on model)possible
- Fault in the battery monitoring unit or control module, or outdated softwarerare
- Internal pack fault causing localised overheatingrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting battery temperatures, ambient temperature and vehicle state when the fault set.
- Look for other battery temperature, cooling fan or high-voltage codes that point to a shared cause.
- Visually inspect the battery cooling air intake, ducting, filters and fan for blockages, debris or damage.
- Compare live temperature readings from all battery sensors after the car has cooled; they should agree closely, so note whether sensor C is the odd one out.
- Inspect the sensor wiring and connectors for damage, corrosion, moisture or loose pins, following the manufacturer's high-voltage safety procedures.
- Check the sensor circuit for open circuit, short circuit and resistance against the manufacturer's specification, only after the high-voltage system is isolated by a trained technician.
- Check the cooling system operation and fan control commands with a scan tool, as the procedure depends on the model.
- Check for software updates or technical bulletins for the vehicle before replacing major components.
How to fix
- Repair or replace damaged wiring or connectors in the sensor circuit.
- Replace the faulty temperature sensor or sensor harness, if the design allows it to be replaced separately.
- Refit or secure a displaced sensor correctly in the pack.
- Clear blockages and repair or replace the battery cooling fan, ducting or cooling components.
- Update the control unit software where a known fault or outdated calibration is the cause, or repair or replace the unit if proven faulty.
- Have a trained technician inspect or repair the battery pack if an internal fault is found.
Can I keep driving?
The car may be driveable for a short time, but power and battery performance can be limited and a real overheating fault could damage the battery. Have it checked soon, and stop driving if a red warning appears, there is a burning smell or the car loses power.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.