P0AC7
Hybrid/EV Battery Temperature Sensor B Circuit Low.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- A
- AreaHybrid propulsion
- C7
- FaultThe specific fault in that area
What it means
P0AC7 means the hybrid or EV battery management system saw the signal from battery temperature sensor 'B' fall below its expected range. This usually points to a short to ground, a wiring fault, or a sensor reading as if it were extremely hot. Which sensor is 'B' and where it sits in the pack depends on the make, model and battery design.
Symptoms
- Hybrid system or battery warning light on the dashboard
- Reduced power or limp mode
- Cooling fans for the battery running constantly or at high speed
- Reduced electric assist or EV range, or the engine running more than normal
- Charging limited or stopped
- Other battery temperature or battery performance codes stored alongside it
Possible causes
- Temperature sensor B faulty (internal short or resistance drifted too low)likely
- Sensor signal wire shorted to ground or chafed against the pack structure or harness routinglikely
- Corroded, damaged or contaminated connector at the sensor or battery monitoring modulepossible
- Water or coolant ingress into the sensor circuit or pack connectorspossible
- Fault in the battery monitoring unit or battery control module input circuitrare
- Outdated or faulty control unit software where the manufacturer has issued a fix for this coderare
How to diagnose
- Read all stored and pending codes with freeze frame data, and note whether other battery temperature or voltage codes are present.
- Check for manufacturer bulletins or software updates relevant to this model and code.
- View live data for all battery temperature sensors and compare sensor B with the others. A reading stuck at an extreme or far from the rest points to the sensor or its circuit.
- Compare the sensor readings with the actual pack temperature after the car has been left to cool, since all sensors should be close to each other.
- Have a suitably trained technician isolate the high-voltage system following the manufacturer's procedure, then inspect the accessible sensor wiring and connectors for damage, corrosion, moisture and pin tension.
- Check the sensor circuit for a short to ground and for correct resistance against the manufacturer's specification, with the system isolated and the connectors disconnected.
- Check the sensor supply and reference voltage at the connector, following the wiring diagram for the model.
- Clear the code after repair and road test, confirming that the sensor reading is plausible and the code does not return.
How to fix
- Replace the faulty temperature sensor or sensor assembly in line with the manufacturer's procedure.
- Repair or replace the damaged wiring section that is shorted to ground, and secure it so it cannot chafe again.
- Clean, dry or replace corroded or wet connectors and fix the source of any water ingress.
- Replace the battery monitoring or control module only if the circuit and sensor are proven good and the manufacturer's tests point to it.
- Update the control unit software if a known fault in the calibration is confirmed.
Can I keep driving?
Medium severity
The car may still drive, but the system may limit power and cannot fully monitor pack temperature, so avoid hard use and long journeys. Have it diagnosed soon, and stop if the warning escalates, a burning smell appears, or the pack becomes noticeably hot.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.