P28EDElectric/Auxiliary Transmission Fluid Pump B Overspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Pump B is a second electrically driven transmission fluid pump that works independently of the engine, for example to hold pressure during start-stop or electric driving, or to feed clutch cooling. P28ED says its motor runs faster than commanded or faster than its permitted maximum. That typically happens when the pump loses its load because it draws air, at low fluid level or with a blocked suction filter, or when the speed estimate of a sensorless motor goes wrong. No manufacturer documents P28ED publicly. Analogous checks exist for single pumps: GM logs P179A on the 2016 Cadillac ELR when the pump motor exceeds its maximum speed of 6500 rpm, Type A, and Ford's 2019 plug-in hybrids flag a speed above 105 percent of command for 3 s under P0B0D. CARB requires functional checks.
- What you may notice
- Transmission warning or check engine light on
- Start-stop or electric driving disabled
- Whining from the pump area
- Likely causes
- LikelyLow fluid level or air drawn in, so the pump runs without load
- PossibleBlocked suction filter or inlet
- PossibleFaulty speed feedback or control in the pump controller
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.