P28ED code meaning
Electric/Auxiliary Transmission Fluid Pump B Overspeed
Powertrain system Generic code P28xx codes Check engine light
What P28ED means
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.
P28ED at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28ED
- Transmission warning or check engine light on
- Start-stop or electric driving disabled
- Whining from the pump area
Common causes of P28ED
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux transmission pump bTransmission fluid
What each part of P28ED means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| ED | The exact fault in that area. |
What to do next
- Note P28ED and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P28ED
What does P28ED mean?
P28ED means "Electric/Auxiliary Transmission Fluid Pump B Overspeed". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P28ED?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P28ED fail an emissions test?
Yes, it can. P28ED is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P28ED to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P28ED clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.