P0B08Electric/Auxiliary Transmission Fluid Pump Motor Phase W 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
- P0B08 is set when the current in phase W of the auxiliary transmission fluid pump motor rises above the permitted limit. No manufacturer documents this exact code in public sources. In GM's 2016 Volt calibration the equivalent protection is P0C28, which fails on any phase above 35 A or on a d-axis current below a temperature-dependent limit, both within milliseconds to protect the IGBTs. A W-specific high code points to a short in the W lead or winding, a binding pump or a sensing error; the Hitachi patent shows the W value may be calculated rather than measured directly. CARB requires such output drivers to be monitored for circuit faults. The pump shuts down, so start-stop and electric driving are restricted. P0B07 is the low side, P0B02 and P0B05 phases U and V.
- What you may notice
- MIL and transmission or hybrid warning
- Auxiliary pump shuts down, auto-stop disabled
- Likely causes
- LikelyPhase W 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 W 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.