C0628Variable Effort Steering Module Performance
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C0628 says the unit that runs variable effort steering fails its own function checks. On GM's Magnasteer that unit was a separate module in 1996–97 and became part of the brake control module from 1998. A GM patent describes the logic: a microcomputer reads coil current from speed and lateral acceleration tables, limits the total and its rate of change and drives the coil by PWM; a Steering Solutions patent gives ±3 A full scale. Performance faults cover a driver stage that cannot reach the commanded current, a failed internal self-test or corrupt calibration. GM's Tech 2 can run a function test sweeping the coil current. No maker publishes C0628 in this sense; GM's PIP5094 list (2014 and older) carries the number with an older meaning.
- What you may notice
- Steering effort no longer changes with speed
- Heavy steering when parking or light steering at highway speed
- Steering, ABS or stability warning where the brake module hosts the function
- Likely causes
- PossibleInternal fault in the controlling module or its coil driver stage
- PossibleLow or unstable supply voltage so the commanded current cannot be reached
- RareCorrupt calibration or software after a module replacement or flash
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.