P0B02 code meaning
Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High
Powertrain system Generic code P0Bxx codes Check engine light
What P0B02 means
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.
P0B02 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B02
- MIL and transmission or hybrid warning
- Auxiliary pump shuts down, auto-stop disabled
- Harsh or delayed engagement after an engine stop
Common causes of P0B02
- Most 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
- Less likelyShorted turns in phase U of the pump motor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux trans pump motor phase uAux trans pump control moduleWiring harness
What each part of P0B02 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B | Area: hybrid propulsion. |
| 02 | The exact fault in that area. |
What to do next
- Note P0B02 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0B02
What does P0B02 mean?
P0B02 means "Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B02?
Drive gently and only to a workshop. With P0B02 the car can go into limp mode (reduced power) to protect itself.
Will P0B02 fail an emissions test?
Yes, it can. P0B02 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0B02 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0B02 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.