U028ALost Communication With Transmission Fluid Pump Module B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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 For B, expect stop-start or electric drive to be withdrawn.
- What you may notice
- Start-stop function no longer active
- Electric driving blocked or engine keeps running
- Transmission warning, harsh engagement after an engine stop
- Likely causes
- 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
- RareTransmission controller software outdated
- 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.