Open circuit or high resistance in the sensor signal or return wiring; Corroded, loose or damaged connector at the battery temperature sensor or battery control unit; Faulty battery temperature sensor (internal open circuit); Short to a voltage supply on the signal wire; Fault in the battery management or hybrid control unit, or its sensor reference supply; Damage to the wiring harness or sensor after battery pack work or impact.

P0ACD

Hybrid/EV Battery Temperature Sensor C Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
A: AreaHybrid propulsion
CD: FaultThe specific fault in that area

What it means

P0ACD means the hybrid or EV control unit has seen the signal from hybrid/EV battery temperature sensor C rise above its expected electrical range. This is normally a sensor voltage reading that is too high, which usually points to an open circuit, a poor connection or a failed sensor. Sensor position and numbering vary by model, so check the manufacturer data to identify which sensor is 'C'.

Symptoms

Hybrid or EV system warning light on the dashboard
Reduced power or limited electric assist or boost
Cooling fan for the traction battery running constantly or not at all
Reduced charging rate or reduced regenerative braking
Poor fuel economy on a hybrid as the system limits battery use
In some cases the car goes into a limp mode or will not enter Ready mode

Possible causes

Open circuit or high resistance in the sensor signal or return wiringlikely
Corroded, loose or damaged connector at the battery temperature sensor or battery control unitlikely
Faulty battery temperature sensor (internal open circuit)likely
Short to a voltage supply on the signal wirepossible
Fault in the battery management or hybrid control unit, or its sensor reference supplyrare
Damage to the wiring harness or sensor after battery pack work or impactpossible

How to diagnose

Read all stored and pending codes plus freeze frame data, and note whether other battery temperature sensor codes are present.
Check the manufacturer data to find which sensor is 'C' on this model and where it is fitted.
Follow high-voltage safety procedures: only suitably trained staff should work near the traction battery, and the system must be isolated before any pack-side connector is disturbed.
Inspect the sensor wiring and connectors for corrosion, pushed-out pins, water ingress, chafing and previous repair damage.
With live data, compare the sensor C temperature against the other battery temperature sensors at a cold soak; an implausible reading such as extreme cold points to an open circuit.
Test the sensor resistance and compare it to the specification for the model, and check the reference voltage, signal and ground at the connector.
Carry out a wiring continuity test and check for short to voltage on the signal wire with the system isolated.
If wiring and sensor test good, check for software updates or known faults on the control unit as per the manufacturer data.

How to fix

Repair or replace damaged wiring and terminals in the sensor circuit.
Clean, reseat or replace corroded or loose connectors.
Replace the battery temperature sensor if it tests out of specification.
Repair any short to voltage on the signal wire.
Replace or reprogram the battery control unit only after the circuit and sensor are proven good and the manufacturer lists it as a known fix.
Clear the code after repair and road test to confirm it does not return.

Can I keep driving?

Medium severity

The car can usually be driven short-term, but the system may limit power and protect the battery, and without a working temperature reading it cannot manage battery heat properly. Have it checked soon, and stop driving if a red warning shows or the car loses drive.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.