P277BElectric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- P277B concerns the power stage that energises the motor of auxiliary pump B, wherever it sits: inside a separate pump controller or in the transmission module. The stage is switched on, but what comes back – current, speed or a status signal – does not fit the command, so the module rates the driver as implausible rather than reporting a plain open or short. No manufacturer documents P277B publicly. For pump A, Ford's 2024 OBD summary (10R60/10R80, 8F57) lists a related case: the pump flags implausible current together with implausible speed, stored as P0C29 (UDS P0C29_92). Overheated or failing driver electronics, a poor ground, low system voltage and a pump that loads the stage abnormally are the usual triggers. The gearbox then runs without the pump's support, which mainly affects stop-start.
- What you may notice
- Transmission warning or service message
- Stop-start unavailable
- Jerky drive-off after engine restarts
- Likely causes
- LikelyFailing output stage in the pump controller or TCM
- PossiblePoor ground or low system voltage at the driver
- PossiblePump motor loading the driver abnormally
- RareLoose or corroded pins between driver and pump
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.