P0AF3

What it means

P0AF3 means the hybrid or electric vehicle control unit saw the signal from drive motor inverter temperature sensor B disagree with expected values or with other temperature readings. The signal is plausible electrically but is out of range, stuck, slow to change, or does not match the other inverter, coolant or motor temperatures. The inverter's temperature is used to protect it, so the control unit may limit power as a precaution.

Symptoms

• Hybrid or EV system warning light on
• Reduced power or limp mode
• Reduced or no electric assist or regeneration
• Cooling fan or inverter coolant pump running harder or longer than normal
• Intermittent loss of drive or the car refusing to go into Ready mode

Possible causes

• Faulty inverter temperature sensor B giving a drifting or stuck readinglikely
• Wiring or connector fault in the sensor circuit (corrosion, high resistance, chafing, poor pin tension)likely
• Low inverter coolant level, air in the system or a weak coolant pump causing real temperature differencespossible
• Blocked or restricted inverter cooling circuit or heat exchangerpossible
• Internal fault in the inverter assembly or its control boardpossible
• Outdated or faulty control unit software where a manufacturer update is known to address the faultrare

How to diagnose

1. Read all stored codes and freeze frame data, noting temperatures, vehicle speed, load and whether other inverter or motor temperature codes are present.
2. Check the inverter coolant level and condition, and look for leaks, using the manufacturer's procedure.
3. Check that the inverter coolant pump and cooling fans run when commanded, and that coolant hoses are not kinked or blocked.
4. Inspect the sensor wiring and connectors for damage, corrosion, water ingress or loose pins, without touching any orange high-voltage cables.
5. Compare the live data for temperature sensor B with sensor A, motor and coolant temperatures on a cold car; they should read similarly after a long soak.
6. Watch the sensor reading while gently moving the harness to find intermittent faults.
7. Test sensor and circuit resistance or voltage against manufacturer specification, as the values depend on the model.
8. Have a trained high-voltage technician check the inverter if the circuit and cooling system are sound.

How to fix

• Repair or replace damaged wiring, terminals or connectors in the sensor circuit.
• Replace the temperature sensor, or the inverter assembly if the sensor is not serviced separately.
• Top up or replace the inverter coolant, and bleed the system using the correct procedure.
• Repair or replace a failed coolant pump, or clear a blocked cooling circuit.
• Apply a manufacturer software update if one is available for this fault.
• Replace the inverter if an internal fault is confirmed by a trained high-voltage technician.

Can I keep driving?

Nearby codes

• P0AF2GenericDrive Motor Inverter Temperature Sensor B Circuit
• P0AF4GenericDrive Motor Inverter Temperature Sensor B Circuit Low