P0A31: Drive Motor B Temperature Sensor Circuit Range/Performance

What it means

The drive motor B temperature sensor signal is outside the expected range or does not perform as expected. The specific cause depends on the vehicle.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

The Drive Motor B temperature sensor reports winding heat so the control module can check it against expected motor operation. P0A31 sets when the reading is outside the expected range or responds implausibly, which can result from sensor drift, ageing, or displaced mounting.

Common causes

Most likely first.

1. Sensor characteristic drifted
2. Sensor mounting displaced
3. Sensor element aged beyond calibration window

Symptoms

• EV/hybrid system warning light on
• Reduced motor power or torque
• Possible limp mode or vehicle shutdown

How to diagnose it

1. Review freeze-frame data and compare Drive Motor B temperature with motor load, speed, and inverter data in live readings.
2. Inspect the Drive Motor B sensor connector and harness for looseness, corrosion, or damage.
3. Check whether the reported temperature changes smoothly as the motor warms and cools, following the manufacturer's procedure.
4. Test the sensor response and circuit against the manufacturer's specification to identify drift or an unstable connection.
5. If the circuit is sound, inspect sensor mounting and check the control module's interpretation of the signal.

Common fixes

• Secure a loose Drive Motor B temperature sensor or connector.
• Clean corroded pins and repair damaged wiring.
• Replace the Drive Motor B sensor if its response is outside the manufacturer's specification.
• Correct displaced sensor mounting if it is affecting the reading.

Can I keep driving?

Drive gently and avoid sustained high load, since the system may reduce Drive Motor B torque when its temperature reading is implausible. Stop if the vehicle enters limp mode or shows a serious hybrid/EV warning.