OBD-II code · Powertrain (generic, extended)
P277A Electric/Auxiliary Transmission Fluid Pump B Hydraulic Leakage
The second auxiliary transmission fluid pump cannot maintain pressure even at high duty cycle. Indicates internal hydraulic leakage downstream of the pump.
Is it safe to drive with P277A?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyWorn or hardened seals downstream of pump
- PossiblePressure relief or bypass valve stuck open
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
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 3–8 h
- Emissions test
- Usually unaffected
- Parts involved
- Aux Trans Pump B, Hydraulic Circuit, Valve Body Seals
Related codes
- P0B0CElectric/Auxiliary Transmission Fluid Pump A Hydraulic Leakage
- P2777Upshift Switch Circuit High
- P2778Upshift Switch Circuit Intermittent/Erratic
- P2779Downshift Switch Circuit Range/Performance
- P277BElectric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
- P277CElectric/Auxiliary Transmission Fluid Pump B Motor Stalled
- P277DElectric/Auxiliary Transmission Fluid Pump B Motor Over Temperature
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.