Chassis, generic

C009F 4WD/AWD Rear Differential Unit Actuator B Position Sensor C

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Third position channel C of actuator B in the rear differential unit is the subject of this code. Its absence is noticed because the remaining channels A and B still produce transitions that C should follow. Woodward's patent shows the method: after an invalid combination the controller waits for the next one, and the sensor whose output did not move in between is the failed one; the motor can then be driven with a substitute third signal. In a rear unit such as BorgWarner's electro-hydraulic coupling, whose brushless actuator motor carries its own electronics, this monitoring sits next to the motor, so the fault may be reported over the bus by an integrated controller. No manufacturer bulletin mentions C009F. Repairs usually mean wiring checks first, then a new actuator motor.

Likely causes

Open or high-resistance channel C line of actuator B
Hall element C of actuator B defective
Fault in electronics integrated in the actuator motor

Symptoms

  • AWD warning lamp
  • Rear torque split or locking function deactivated

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,200
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

rear diff actuator b pos c

Related codes

C009DC009EC00A0C009B

References: patents.google.com, borgwarner.com, ti.com.