C059A code meaning
Power Steering Control Module - Rear Missing Calibration
What C059A means
C059A concerns active rear-axle steering: its control module lacks the calibration it needs to position the rear wheels. Systems like ZF's AKC turn the rear wheels by a few degrees with an electrically driven spindle, either through one central actuator or one per wheel. A Magna patent shows what has to be calibrated: a coarse absolute travel sensor and a fine rotor sensor are referenced to the geometric centre between both mechanical end stops, and these values are stored so the actuator can return to straight-ahead. Without them the module cannot hold the rear wheels centred and disables rear steering. No maker documents C059A publicly. GM names the part K92 Rear Power Steering Control Module; on the 2024 Hummer EV it stopped working after vehicle-wide programming until authentication was repeated (PIT6350), logged as U3000/U1961/U1962.
C059A at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C059A
- Rear steering warning in the cluster and rear wheel steering inactive
- Larger turning circle and changed handling at speed
- Steering wheel slightly off centre on straight roads
Common causes of C059A
- Most likelyRear steering module or actuator replaced without centre calibration
- PossibleProgramming or setup after a software update not completed
- PossibleSuspension or alignment work requiring a new rear steering zero point
- Less likelyLow 12 V supply interrupting the calibration routine
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Rear eps moduleRear steering actuator
What each part of C059A means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9A | The exact fault in that area. |
What to do next
- Note C059A 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 C059A
What does C059A mean?
C059A means "Power Steering Control Module - Rear Missing Calibration". C059A concerns active rear-axle steering: its control module lacks the calibration it needs to position the rear wheels. It is a generic code, so it means the same on every make.
Is it safe to drive with C059A?
Drive gently and only to a workshop. With C059A the car can go into limp mode (reduced power) to protect itself.
Will C059A fail an emissions test?
C059A 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 C059A to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will C059A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.