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.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- MIL and transmission or hybrid warning
- Auxiliary pump shuts down, auto-stop disabled
- Harsh or delayed engagement after an engine stop
Most likely causes
- Phase U lead shorted to another phase or to ground
- Pump binding mechanically, raising motor current
- Current sensing in the pump inverter reads too high
- Shorted turns in phase U of the pump motor
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0B02 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- 02: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0B02?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0B02?
The most common causes are: phase U lead shorted to another phase or to ground; pump binding mechanically, raising motor current; current sensing in the pump inverter reads too high.
Related codes
- P0B00Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current
- P0B01Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current Low
- P0B05Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current High
- P0B08Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current High
- P0C22Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit High
- P0C28Electric/Auxiliary Transmission Fluid Pump A Motor Current High
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.