What it means
The drive motor B rotor position sensor reports a circuit intermittent 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 supplies rotor-angle information used to time motor phase switching. This code is set when that signal or its circuit becomes intermittent, so the module cannot depend on position data consistently.
Common causes
Most likely first.
- Connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
Symptoms
- EV/hybrid system warning light on
- Reduced motor power or torque
- Possible limp mode or vehicle shutdown
How to diagnose it
- Save freeze-frame data and check stored or pending codes and live drive motor B position readings for drop-outs around the time the fault occurred.
- With the hybrid system powered down under the manufacturer's high-voltage safety procedure, check that the drive motor B sensor connector is fully seated and its lock is intact.
- Inspect the connector pins, harness, and strain points for looseness, corrosion, rubbed insulation, or damage that could open under vibration.
- Use the manufacturer's procedure to test sensor ground stability and signal continuity while gently moving the low-voltage harness to reproduce an intermittent fault.
- Compare sensor output with rotor speed during a controlled operating check and look for brief drop-outs or spikes.
- If the harness and ground remain stable, test the sensor itself for an intermittent internal fault using the manufacturer's specification.
Common fixes
- Reseat and secure the drive motor B position-sensor connector.
- Repair loose, corroded, or damaged connector terminals.
- Repair chafed wiring or a noisy or unstable sensor ground.
- Replace the drive motor B sensor if its signal drops out intermittently despite sound wiring.
Can I keep driving?
Treat intermittent power loss or limp mode as a reason to stop driving, since the fault can recur without warning and compromise motor torque control. If symptoms are absent, keep driving to a minimum and avoid routes where a sudden loss of propulsion would be hazardous.
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.