P0B03 code meaning
Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current
Powertrain system Generic code P0Bxx codes Check engine light
What P0B03 means
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.
P0B03 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 P0B03
- MIL or transmission/hybrid warning
- Engine auto-stop or electric mode no longer available
Common causes of P0B03
- Most 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
- Less likelyWinding fault in phase V 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 vAux trans pump control moduleWiring harness
What each part of P0B03 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. |
| 03 | The exact fault in that area. |
What to do next
- Note P0B03 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 P0B03
What does P0B03 mean?
P0B03 means "Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current". P0B03 covers a general current fault in phase V of the brushless motor of the electric auxiliary transmission fluid pump. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B03?
Drive gently and only to a workshop. With P0B03 the car can go into limp mode (reduced power) to protect itself.
Will P0B03 fail an emissions test?
Yes, it can. P0B03 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 P0B03 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0B03 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.