P277B code meaning
Electric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
Powertrain system Generic code P27xx codes Check engine light
What P277B means
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.
P277B at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P277B
- Transmission warning or service message
- Stop-start unavailable
- Jerky drive-off after engine restarts
Common causes of P277B
- Most likelyFailing output stage in the pump controller or TCM
- PossiblePoor ground or low system voltage at the driver
- PossiblePump motor loading the driver abnormally
- Less likelyLoose or corroded pins between driver and pump
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aux trans pump b driverControl module
What each part of P277B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| 7B | The exact fault in that area. |
What to do next
- Note P277B 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 P277B
What does P277B mean?
P277B means "Electric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P277B?
Drive gently and only to a workshop. With P277B the car can go into limp mode (reduced power) to protect itself.
Will P277B fail an emissions test?
P277B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P277B to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P277B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.