What it means
The drive motor B rotor position sensor reports a circuit low fault. Phase commutation cannot be controlled reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Drive motor B's position sensor reports rotor position so the hybrid control system can switch motor phases at the right time. This code is set when the monitored sensor circuit voltage stays below the expected range, which can prevent reliable motor commutation.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- EV/hybrid system warning light on
- Reduced motor power or torque
- Possible limp mode or vehicle shutdown
How to diagnose it
- Capture freeze-frame data and check drive motor B position-sensor live readings for a persistently low value or drop-out.
- With the vehicle powered down using the manufacturer's high-voltage safety procedure, inspect the drive motor B sensor connector for corrosion, moisture, bent pins, or a loose fit.
- Inspect the signal wire between the sensor and control module for chafing or contact with ground, especially near connectors and moving or hot components.
- Use the manufacturer's wiring diagram and procedure to test for a signal wire short to ground and check sensor supply and ground integrity.
- Measure the circuit at the sensor and module ends to isolate a wiring fault from an internal sensor short, comparing results with the manufacturer's specification.
- If wiring and connections pass, test or substitute the drive motor B sensor only as allowed by the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose drive motor B sensor connector pins, replacing damaged terminals.
- Repair a signal wire shorted to ground or damaged harness section.
- Restore a poor sensor supply or ground connection.
- Replace the drive motor B position sensor if it is internally shorted or fails the manufacturer's specification.
Can I keep driving?
Do not continue a trip if the vehicle has reduced propulsion, enters limp mode, or shows signs it may shut down; the drive motor B signal may not support dependable torque control. If there are no driving symptoms, keep use brief and avoid high-speed or high-load driving until diagnosed.
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.