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.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Aux trans pump b
- Hydraulic circuit
- Valve body seals
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Worn or hardened seals downstream of pump
- Pressure relief or bypass valve stuck open
Possible 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
Diagnostic notes
- The malfunction indicator lamp may illuminate
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.