P28D9Clutch B Motor Underspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28D9 indicates that the clutch B motor cannot reach the speed it is commanded to, leaving the pump short of flow to raise or adjust clutch pressure. Getrag states that its pump actuators control pressure consistently down to low temperatures, so a motor that persistently lags points to extra drag rather than normal cold behaviour: particles caught in the gerotor, a tight bearing, or oil of the wrong grade. Stellantis names jammed actuator pumps on the 7HDT300 in bulletin 21-040-26, but lists P28D5 there, not P28D9. On the electrical side a weak supply or a driver stage that reduces output due to heat, logged as P28D6, can also hold the motor back. Excess speed is P28D8; P28CA is the clutch A version. No threshold is public.
- What you may notice
- Delayed or jerky engagement of clutch B
- Fault more likely after standing in the cold
- Clutch B gears may be withheld
- Likely causes
- LikelyParticles caught in the clutch B gerotor pump
- PossibleTight or damaged bearing in the clutch B motor or pump
- RareIncorrect transmission fluid with too high viscosity
- RareLow supply voltage or poor ground at the actuator
- 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 – €1,600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.