P0B08 code meaning
Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current High
Powertrain system Generic code P0Bxx codes Check engine light
What P0B08 means
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.
P0B08 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 P0B08
- MIL and transmission or hybrid warning
- Auxiliary pump shuts down, auto-stop disabled
Common causes of P0B08
- Most 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
- Less likelyShorted turns in phase W 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 wAux trans pump control moduleWiring harness
What each part of P0B08 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. |
| 08 | The exact fault in that area. |
What to do next
- Note P0B08 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 P0B08
What does P0B08 mean?
P0B08 means "Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current High". P0B08 is set when the current in phase W of the auxiliary transmission fluid pump motor rises above the permitted limit. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B08?
Drive gently and only to a workshop. With P0B08 the car can go into limp mode (reduced power) to protect itself.
Will P0B08 fail an emissions test?
Yes, it can. P0B08 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 P0B08 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0B08 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.