P0AF5

What it means

P0AF5 means the hybrid or electric vehicle control unit has seen the signal from drive motor inverter temperature sensor B reading too high in voltage, outside its normal range. These sensors are usually thermistors, so a high voltage reading normally points to an open circuit, a short to voltage or a failed sensor. With the sensor unreliable, the system cannot properly monitor inverter temperature and may limit power to protect the inverter.

Symptoms

• Hybrid or EV system warning light or malfunction message on the dashboard
• Reduced power or limp-home mode
• Reduced or restricted acceleration, especially under load
• Cooling fan or pump running harder than normal, or at an odd time
• Vehicle refusing to enter Ready mode or shutting down the drive system in some cases

Possible causes

• Open circuit or high resistance in the sensor B signal or ground wiringlikely
• Corroded, loose or damaged connector terminals at the sensor or inverterlikely
• Faulty inverter temperature sensor B (often part of the inverter assembly, so replacement options depend on the model)possible
• Short to a voltage supply in the sensor signal wiringpossible
• Fault inside the inverter or motor control module's sensor circuitrare
• Outdated or faulty control unit software, where the manufacturer has a known issue for that modelrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting whether other inverter, motor or cooling codes are present.
2. Check for manufacturer service bulletins or software updates relevant to the model and the code.
3. Using live data, compare the inverter temperature readings, including sensor B, against the other sensors and the ambient temperature. A sensor B value stuck at an extreme reading suggests a circuit fault.
4. Visually inspect the accessible wiring and connectors for chafing, water ingress, corrosion, bent pins or poor terminal tension. Only a trained technician should work near high-voltage parts, following the manufacturer's isolation procedure.
5. With the system safely isolated and the connector disconnected, check the sensor circuit for continuity, short to voltage and short to ground, and check the reference supply and ground, using the model's wiring diagram.
6. Measure the sensor resistance and compare it with the manufacturer's specification at a known temperature, if the sensor can be tested.
7. Wiggle-test the harness while watching live data to find intermittent faults.
8. If wiring and sensor are good, assess the inverter or control module following manufacturer diagnostic procedures.

How to fix

• Repair or replace damaged wiring in the sensor B circuit, using the proper repair method for the harness.
• Clean, repair or replace corroded or damaged connector terminals and reseat the connectors securely.
• Replace the inverter temperature sensor or the inverter assembly if the sensor is not serviceable separately and has failed.
• Repair any short to voltage in the harness and then recheck the sensor readings.
• Update the control unit software only if the manufacturer lists it as a fix for this fault.
• Replace or repair the inverter or control module if testing confirms an internal circuit fault.

Can I keep driving?

Nearby codes

• P0AF4GenericDrive Motor Inverter Temperature Sensor B Circuit Low
• P0AF6GenericDrive Motor Inverter Temperature Sensor B Circuit Intermittent/Erratic