P0B02Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0B02 reports excessive current in phase U of the auxiliary transmission fluid pump motor, an overcurrent condition that the pump inverter must cut off to protect its switches. No manufacturer documents this exact code publicly. GM handles the same case differently: on the Volt and later hybrids it sets P0C28 when the absolute current of any phase exceeds 35 A for a few milliseconds, Type A. A phase-specific high code therefore points to a shorted U lead, a shorted winding, a jammed pump or a U current sensor reading too high. The Hitachi idle-stop pump patent shows phase currents being reconstructed from one bus shunt, which makes a sensing error a real candidate. The pump usually stops; auto-stop or electric driving is blocked. P0B01 is the low side, P0B05 and P0B08 the same fault on V and W.
- What you may notice
- MIL and transmission or hybrid warning
- Auxiliary pump shuts down, auto-stop disabled
- Harsh or delayed engagement after an engine stop
- Likely causes
- LikelyPhase U lead shorted to another phase or to ground
- PossiblePump binding mechanically, raising motor current
- PossibleCurrent sensing in the pump inverter reads too high
- RareShorted turns in phase U of the pump motor
- 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: €200 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.