U028A code meaning
Lost Communication With Transmission Fluid Pump Module B
Network system Generic code U02xx codes Check engine light
What U028A means
An electric transmission fluid pump with built-in electronics holds clutch pressure and lubrication whenever the engine is stopped, in auto stop or electric driving. Module B is a second pump of this kind; U028A means the transmission or hybrid controller no longer hears its status frames. No manufacturer documents U028A or names a pump B publicly, so the reaction must be inferred from pump A. Stellantis calls that unit transmission fluid pump module 1 and ties U0287 on the Wrangler and Grand Cherokee 4xe to a failed in-pan pump with MIL and limp mode (21-041-26). Hyundai stores U028700 in the transmission unit of the Santa Fe and Tucson without any warning lamp and merely blocks Idle Stop and Go (26-AT-002H). For B, expect stop-start or electric drive to be withdrawn.
U028A at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of U028A
- Start-stop function no longer active
- Electric driving blocked or engine keeps running
- Transmission warning, harsh engagement after an engine stop
Common causes of U028A
- Most likelyElectric pump B or its integrated electronics failed
- PossibleCorroded or loose pump connector, oil wicking into the connector
- PossibleSupply, ground or bus line to pump B interrupted
- Less likelyTransmission controller software outdated
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission fluid pump module bVehicle bus wiring
What each part of U028A means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 8A | The exact fault in that area. |
What to do next
- Note U028A 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 U028A
What does U028A mean?
U028A means "Lost Communication With Transmission Fluid Pump Module B". An electric transmission fluid pump with built-in electronics holds clutch pressure and lubrication whenever the engine is stopped, in auto stop or electric driving. It is a generic code, so it means the same on every make.
Is it safe to drive with U028A?
Drive gently and only to a workshop. With U028A the car can go into limp mode (reduced power) to protect itself.
Will U028A fail an emissions test?
Yes, it can. U028A 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 U028A to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U028A clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.