C0091 code meaning
4WD/AWD Power Transfer Unit Position Sensor A
What C0091 means
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.
C0091 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0091
- AWD/4WD warning lamp on
- Default torque split or 2WD mode
- Inconsistent AWD engagement
Common causes of C0091
- Most likelyPosition sensor A failed or out of range
- PossibleHarness or connector fault
- Less likelyActuator not reaching expected position
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ptu pos sensor a
What each part of C0091 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 91 | The exact fault in that area. |
What to do next
- Note C0091 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0091
What does C0091 mean?
C0091 means "4WD/AWD Power Transfer Unit Position Sensor A". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with C0091?
Drive gently and only to a workshop. With C0091 the car can go into limp mode (reduced power) to protect itself.
Will C0091 fail an emissions test?
C0091 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0091 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C0091 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.