P0AF4
Drive Motor Inverter 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
- F4
- FaultThe specific fault in that area
What it means
P0AF4 means the hybrid or electric vehicle control unit has seen the signal from drive motor inverter temperature sensor B fall below its expected range. This usually points to a short to ground in the sensor circuit or a failed sensor. The control unit can no longer trust the inverter temperature reading, so it may limit power to protect the inverter. Sensor location and the exact voltage thresholds depend on the model.
Symptoms
- Warning lights on the dashboard, such as the hybrid or EV system warning or the malfunction indicator
- Reduced power or limp mode
- Reduced acceleration or limited top speed
- Cooling fan or coolant pump running harder than normal
- Inverter temperature reading that is implausibly low or does not change
- Vehicle refusing to enter ready mode or shutting down the drive system in some cases
Possible causes
- Wiring fault: sensor signal wire chafed or shorted to ground, or shorted to the sensor ground wirelikely
- Faulty inverter temperature sensor B (internal short or drifted resistance)likely
- Water ingress, corrosion or damaged pins in the sensor or inverter connectorpossible
- Internal fault in the inverter assembly where the sensor is built in and not serviced separatelypossible
- Fault in the control unit input circuit reading the sensorrare
- Previous repair or collision damage to the harness near the inverterrare
How to diagnose
- Read all stored and pending codes and the freeze frame data. Note whether other inverter, motor or cooling codes are present, especially other temperature sensor codes.
- Follow the manufacturer's high-voltage safety procedure. Only a suitably trained technician should work around the inverter and orange cabling.
- Visually inspect the sensor harness and connectors for chafing, water, corrosion, bent or pushed-back pins and signs of previous repair.
- Compare live inverter temperature sensor B data with sensor A, the coolant temperature and ambient temperature after a cold soak. A sensor B reading far below the others suggests a circuit or sensor fault.
- With the system safely isolated and the connector disconnected, check the sensor resistance and the harness for a short to ground against the manufacturer's data.
- Check the reference voltage and ground at the control unit side of the connector. If the code clears or the reading changes with the sensor unplugged, the fault is probably in the sensor.
- Check the inverter coolant level, pump operation and for any related cooling system faults, as these can accompany the temperature data problem.
- Clear the code and road test while watching the live data to confirm whether the fault returns and under what conditions.
How to fix
- Repair or replace the damaged wiring, correcting any short to ground, and secure the harness away from sharp edges.
- Clean, dry and repair the connector, or replace it if the terminals are corroded or damaged.
- Replace the temperature sensor if it is serviceable separately and tests faulty.
- Replace or repair the inverter assembly if the sensor is integral and has failed, following the manufacturer's procedure.
- Replace or update the control unit only if testing proves the input circuit has failed or the manufacturer lists a calibration for this fault.
Can I keep driving?
The car may be driven carefully for a short time, but expect reduced power and a risk of the drive system shutting down. Get it diagnosed soon, as the inverter's overheating protection is working with unreliable data.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.