P0ACE
Hybrid/EV Battery Temperature Sensor C Circuit Intermittent/Erratic.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- A
- AreaHybrid propulsion
- CE
- FaultThe specific fault in that area
What it means
P0ACE is a generic powertrain code meaning the hybrid or EV battery control unit has seen an intermittent or erratic signal from hybrid/EV battery temperature sensor C. The reading jumped, dropped out or changed implausibly quickly compared with the other pack temperature sensors or with expected thermal behaviour. Which part of the pack sensor C monitors depends on the make and model.
Symptoms
- Hybrid or EV system warning light, or malfunction indicator lamp, on
- Reduced power or limited acceleration
- Reduced regenerative braking or limited charging
- Cooling fan for the battery running louder or more often than normal
- Reduced electric range or the engine running more often on a hybrid
- Intermittent fault that comes and goes with vibration or temperature
Possible causes
- Loose, corroded or damaged connector at the battery temperature sensor or battery control unitlikely
- Chafed, stretched or broken wiring in the sensor harness causing intermittent open or short circuitlikely
- Faulty battery temperature sensor giving erratic readingspossible
- Moisture or contamination in the battery pack connectors or sensor harnesspossible
- Fault in the battery monitoring or control unit, or its sensor supply or reference voltagerare
- Outdated control unit software where the manufacturer has published a fix for this faultrare
How to diagnose
- Read all stored and pending codes and note any other battery temperature, cooling fan or high-voltage system codes
- Review freeze frame data and note battery state of charge, temperatures and operating conditions when the fault set
- Follow the manufacturer's high-voltage safety procedure before touching any pack wiring, and only let suitably trained staff work on high-voltage components
- Inspect the sensor wiring and connectors for damage, corrosion, moisture, looseness or poor pin tension
- Watch live data from sensor C alongside the other pack temperature sensors and look for spikes, dropouts or readings that differ greatly
- Wiggle-test the harness and connectors with the data live to see if the reading becomes erratic
- Check the sensor circuit resistance, supply and signal voltage against manufacturer specifications, as values vary by model
- Check for software updates or technical bulletins for the model and clear the code, then road test to see if it returns
How to fix
- Repair or replace damaged wiring and clean or refit connectors, replacing any with damaged terminals
- Replace the faulty battery temperature sensor or sensor assembly as the manufacturer specifies
- Dry out and seal any areas with moisture ingress and fix the source of the leak
- Replace or repair the battery control unit only after the wiring and sensor have been proved good
- Update the control unit software where an update is available for this fault
Can I keep driving?
The car can usually be driven short distances, but power and charging may be limited and the battery cannot be monitored accurately. Have it checked soon, and stop driving if a red warning appears, you notice a burning smell, or the pack overheats.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.