Chassis, generic

C0091 4WD/AWD Power Transfer Unit Position Sensor A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Covers position sensor A of the power transfer unit actuator, which reports how far the transfer-case or coupling actuator has moved so the controller can close the loop on torque split or mode. The controller commands the actuator and reads this sensor to confirm the achieved position; this code is set when the sensor signal is out of range, open, shorted or implausible against the commanded or expected position. AWD coupling patents describe electronically controlled couplings whose controller relies on actuator position feedback to meter clutch engagement force. A fault makes the controller unable to trust the actuator position, so it may default to a safe torque split or two-wheel drive and set the AWD/4WD warning lamp; braking and ABS are unaffected.

Likely causes

Position sensor A failed or out of range
Harness or connector fault
Actuator not reaching expected position

Symptoms

  • AWD/4WD warning lamp on
  • Default torque split or 2WD mode
  • Inconsistent AWD engagement

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–1,600
Time1–4 h

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

Parts involved

ptu pos sensor a

Related codes

C0090C0092C0093

References: patents.google.com, en.wikipedia.org.