C00994WD/AWD Rear Differential Unit Actuator A Position Sensor A
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- The title gives actuator A of the rear differential unit three position channels, A to C. That layout matches the way brushless actuator motors track their rotor: three Hall elements on the stator read a magnet on the rotor, and their combined states step the motor through six commutation phases. C0099 concerns channel A alone. It is logged when that signal drops out, sticks or leaves its voltage window, typically from an open wire, a short to ground or a dead Hall element. Schaeffler patents a sensor carrier of this kind for a clutch actuator motor, TI documents Hall-based commutation, and BorgWarner drives its current AWD coupling with a brushless motor. No manufacturer publishes a C0099 case. Losing one channel usually means the rear clutch is released and an AWD warning appears.
- What you may notice
- AWD/4WD warning lamp or message in the cluster
- Rear axle no longer driven, front-wheel drive only
- Reduced traction on slippery surfaces
- Likely causes
- LikelyOpen or grounded signal wire of channel A between actuator and module
- PossibleCorroded or loose connector at the rear drive unit
- PossibleFailed Hall element A inside the actuator motor
- RareMissing sensor supply or ground from the module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,100
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.