P277B
Electric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
The driver stage for the second auxiliary transmission fluid pump does not respond to commands within tolerance.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Aged driver shows degraded switching behaviourPossible
- Current feedback loop noisyPossible
Parts involved
- Aux Trans Pump B Driver
- Control Module
P277B is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.