P0AF2

What it means

P0AF2 means the hybrid or electric vehicle control unit has detected a fault in the circuit of drive motor inverter temperature sensor B. The sensor signal was outside the expected range, such as open circuit or short, or did not agree with other temperature readings. The inverter relies on this sensor to protect itself from overheating, so the system may limit power. Sensor location and testing values depend on the vehicle.

Symptoms

• Warning light on the dashboard, often with a hybrid or EV system warning message
• Reduced power or limp mode
• Reduced regenerative braking or limited charging or boost from the traction battery
• Inverter or motor cooling fan or pump running harder than normal
• Vehicle slow to enter or unable to enter ready mode in some cases

Possible causes

• Wiring or connector fault in the inverter temperature sensor circuit (open circuit, short, corrosion or loose pin)likely
• Faulty temperature sensor inside the inverter assemblylikely
• Fault in the inverter control board or the control unit reading the sensorpossible
• Low coolant level, air in the system or a weak inverter coolant pump causing real overheating that disagrees with other sensorspossible
• Water ingress or contamination at the sensor connector or inverter housingpossible
• Outdated or faulty control unit software where the manufacturer has identified it as a causerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting temperatures, vehicle speed and ready status when the code set
2. Check for related codes for other inverter or motor temperature sensors, coolant pump or high voltage system faults
3. Check the inverter coolant level and condition on a cold system, and look for leaks, following the manufacturer's procedure
4. Visually inspect the sensor wiring and connectors for chafing, corrosion, moisture and poor pin tension, after making the vehicle safe
5. Compare live inverter sensor B temperature with the other inverter and coolant temperature readings on a cold vehicle; they should be close together
6. Check the sensor reference voltage, signal and ground, and sensor resistance, against the manufacturer's data. Only trained staff using the correct high voltage isolation procedure should work near the inverter
7. Check for manufacturer service bulletins or software updates relevant to this code and vehicle
8. Clear the code and road test to see whether it returns, and recheck the live data

How to fix

• Repair or replace damaged wiring and clean or replace corroded or loose connectors
• Replace the temperature sensor if it is serviceable on its own, otherwise replace the inverter assembly
• Top up and bleed the cooling system, repair leaks and replace the coolant pump if it is weak or failed
• Dry out and seal any water ingress, and fix the source of the moisture
• Update the control unit software only if the manufacturer lists it as a fix for this fault

Can I keep driving?

Nearby codes

• P0AF1GenericDrive Motor Inverter Temperature Sensor A Circuit Intermittent/Erratic
• P0AF3GenericDrive Motor Inverter Temperature Sensor B Circuit Range/Performance