What it means
The control module detects a low electrical signal in the drive motor inverter temperature sensor B circuit. This indicates a circuit or sensor signal fault, not necessarily that the inverter is too cold.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Temperature sensor B sends an electrical signal representing drive motor inverter temperature to the control module. P0AF4 sets when that signal is lower than the circuit’s expected electrical range; it does not by itself mean the inverter is unusually cold.
Common causes
Most likely first.
- Signal wire shorted to ground
- Sensor internally shorted
- Poor connector contact
Symptoms
- EV/hybrid system warning light on
- Reduced motor power or torque
- Possible limp mode or vehicle shutdown
How to diagnose it
- Check freeze-frame and live data for sensor B and note whether its signal is pinned low, then review related hybrid-system codes.
- With the vehicle powered down using the manufacturer’s high-voltage safety procedure, inspect sensor B’s connector and wiring for a signal wire touching ground, corrosion, or a loose terminal.
- Check the sensor B signal wire for a short to ground and inspect connector contacts for unwanted bridging or poor fit.
- Test sensor B and the circuit using the manufacturer’s diagnostic steps to determine whether the sensor is internally shorted or the wiring is pulling the signal low.
- After repairing the fault, confirm sensor B’s live reading responds normally and the code does not return.
Common fixes
- Repair a sensor B signal wire that is shorted to ground.
- Clean, tighten, or repair poor contact at the sensor B connector.
- Replace sensor B if testing confirms an internal short.
- Repair any other damaged section of the sensor B circuit identified by testing.
Can I keep driving?
Avoid normal or demanding driving because the hybrid system may restrict torque or shut down. If the vehicle loses power or enters limp mode, pull over safely and arrange service.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.