P0B03Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0B03 covers a general current fault in phase V of the brushless motor of the electric auxiliary transmission fluid pump. No manufacturer publicly describes a monitor for it. GM's 2013 eAssist (BAS Plus) tables name P0B03 only once, as a code that must be inactive before another speed check runs, without a description of its own. In GM's Volt and CT6 tables phase V is watched by the low-side code P0B04, and any overcurrent goes to P0C28. A GM, BMW and Daimler patent on a hybrid transmission pump explains why the pump matters: it must hold transmission pressure when the engine is stopped, otherwise gear engagement can be lost. The general code is a catch-all for implausible V current that fits neither low nor high. P0B04/P0B05 are the low and high variants, P0B00 and P0B06 phases U and W.
- What you may notice
- MIL or transmission/hybrid warning
- Engine auto-stop or electric mode no longer available
- Likely causes
- LikelyPoor contact in the phase V lead or pump connector
- PossibleCurrent sensing in the pump inverter faulty
- PossiblePhase V power stage in the pump control module faulty
- RareWinding fault in phase V 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: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.