What it means
The hybrid control module has not learned the rotor position offset for drive motor B. Phase commutation cannot be optimised until learning completes.
At a glance
- Usually lights the check-engine light
How it works
The rotor position sensor provides the hybrid control module with Drive Motor B’s rotor angle so it can time the motor’s electrical phases. P0C18 means the module has not learned the required position offset, so motor control may be limited until the vehicle-specific learn procedure completes.
Common causes
Most likely first.
- Adaptation lost after battery disconnect
- Sensor replaced without learn procedure
Symptoms
- EV/hybrid system warning light on
- Reduced motor power or torque
- Possible limp mode or vehicle shutdown
How to diagnose it
- Scan all hybrid-system codes and review freeze-frame data to see whether the learn status changed after a battery disconnect or related repair.
- Check service history for recent replacement or work on Drive Motor B’s position sensor, motor, inverter, or associated wiring.
- Inspect the Drive Motor B position-sensor connector and harness for loose pins, corrosion, damage, or poor routing.
- Use a scan tool that supports the vehicle’s position-sensor learning function and check whether the module permits the procedure to start.
- Perform the manufacturer’s learn procedure, then rescan and confirm that Drive Motor B’s offset is learned and the code does not return.
Common fixes
- Complete the manufacturer’s Drive Motor B position-sensor learn procedure.
- Reconnect or repair the Drive Motor B sensor connector or wiring.
- Correct a related sensor or motor installation issue identified by diagnostics.
- Replace a confirmed faulty position sensor or repair the control system if it cannot retain the learned offset.
Can I keep driving?
Driving may be possible, but Drive Motor B torque can be reduced and hybrid operation may become limited. Avoid demanding acceleration and stop if power becomes unpredictable or a hybrid warning escalates.
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.