P28D8Clutch B Motor Overspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28D8 sets when the clutch B motor spins faster than the controller expects for the commanded pressure. A gerotor works by positive displacement, the EVS32 model uses one with a seven-tooth outer rotor, so in a sealed clutch circuit its speed should fall once pressure is built; a motor that keeps accelerating means oil is escaping or the pump has lost its load. Plausible reasons are a worn piston or rotary seal in the clutch B circuit, aeration from low oil, or a sheared drive between motor shaft and inner rotor. A false speed reading from the rotor position sensor can mimic the same, so P28DA and P28DB should be cleared first. Slow running is P28D9; on clutch A the code is P28C9. No limits are published.
- What you may notice
- Clutch B does not hold full torque, flaring on shifts
- Transmission warning and limited gears
- Likely causes
- LikelyWorn piston or rotary feedthrough seal letting oil escape from the clutch B circuit
- PossibleAerated oil due to low level, pump runs without load
- RareSheared drive between clutch B motor shaft and inner rotor
- RareRotor position sensor reporting an excessive speed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.