P0ACA
Hybrid/EV Battery Temperature Sensor C Circuit.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- A
- AreaHybrid propulsion
- CA
- FaultThe specific fault in that area
What it means
P0ACA is a generic code meaning the hybrid or EV battery control unit has detected a fault in the circuit of battery temperature sensor 'C'. The control unit saw a signal outside the expected range, such as an implausible, stuck, open-circuit or short-circuit reading. Which pack location sensor 'C' refers to depends on the vehicle, so check the manufacturer data for the model.
Symptoms
- Hybrid system or battery warning light on the dashboard
- Reduced power or limited electric assist
- Reduced regenerative braking or limited charging
- Battery cooling fan running constantly or not at all
- Reduced electric-only driving range or the engine running more often than usual
- Other battery temperature or battery management codes stored alongside
Possible causes
- Faulty battery temperature sensor C (internal open circuit, short circuit or drift)likely
- Damaged wiring, chafing or broken wires in the sensor circuitlikely
- Corroded, loose or contaminated connector at the sensor or battery packlikely
- Fault in the battery monitoring or control unit input circuitpossible
- Water ingress or damage to the battery pack or its harness after an impact or floodpossible
- Fault in the battery cooling system causing a genuine temperature mismatch that the sensor reading disagrees withrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting any other battery temperature, cooling or voltage codes.
- Compare the live data for all battery temperature sensors at a cold start. They should read similarly, so look for sensor C being stuck, extreme or erratic.
- Check for any warning signs of battery damage, water ingress or previous repair work around the pack, and check that the cooling air intake and fan are clear.
- Visually inspect the accessible harness and connectors for chafing, corrosion, bent pins or poor locking. Do not open or touch high-voltage components unless trained and qualified.
- Following the manufacturer procedure and the correct high-voltage isolation steps, measure the sensor resistance and compare it with the specification for the model.
- Check the sensor circuit for continuity, short to earth and short to supply, and wiggle-test the harness while monitoring live data.
- Check the supply and reference voltage at the control unit connector, per the wiring diagram, to rule out a control unit fault.
- Check for software updates or technical bulletins for the model before replacing the control unit.
How to fix
- Replace the faulty battery temperature sensor, or the part of the pack that includes it, as specified by the manufacturer.
- Repair or replace damaged wiring and ensure it is routed and secured correctly.
- Clean, repair or replace corroded or damaged connectors and terminals.
- Repair the cooling fan or ducting if blockage or failure is contributing.
- Replace or repair the battery control unit only after the wiring and sensor have been proven good, applying any updated calibration if the manufacturer lists one for this fault.
- Clear the code after repair and road test to confirm it does not return.
Can I keep driving?
The car can often be driven for a short time, but the system may limit power and charging, and without a reliable temperature reading the battery cannot be protected properly. Have it checked soon, and stop if a hybrid system overheating or high-voltage battery warning appears, or the car loses power.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.