Chassis, generic

C059A Power Steering Control Module - Rear Missing Calibration

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Rear steering module or actuator replaced without centre calibration
Programming or setup after a software update not completed
Suspension or alignment work requiring a new rear steering zero point
Low 12 V supply interrupting the calibration routine

Symptoms

  • 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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–500
Time0.5–2 h

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

Parts involved

rear eps modulerear steering actuator

Related codes

C0599C0051

References: zf.com, patents.google.com, static.nhtsa.gov.