P284CShift Fork D Stuck
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P284C applies when fork D, the fourth of the generic shift forks, fails to answer an actuation request. Whether the drive is hydraulic, as in most wet dual-clutch boxes, or electric, as in automated manuals with motor-driven drums, the module sees the request but no travel at the position sensor. No manufacturer documentation for P284C is public. Mercedes-Benz, for example, lists several fork D sensor codes for the 8G-DCT (724.1) and even a fifth fork E, yet no stuck code for D. The requirement comes from CARB 13 CCR 1968.2, which demands functional monitoring of transmission parts. A stuck fork usually forces an emergency program with few gears; repairs can range from an actuator or valve body to a full gearbox overhaul.
- What you may notice
- Gears of fork D unavailable or stuck engaged
- Emergency program, reduced speed
- Warning in the instrument cluster
- Likely causes
- LikelyFork D actuator motor or hydraulic valve failed
- PossibleShift drum or rod binding at fork D
- RareModule output stage not driving the fork D actuator
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €300 – €4,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.