P0877Transmission Fluid Pressure Sensor/Switch D Circuit Low
- Generic OBD-II code · Powertrain
- Can trigger limp mode
- How the car detects it
- Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. They are more widespread than A and B: GM's 6L80/6L90 and 6T40/6T70 six-speeds put switch C on the 2-6 brake and D on the 1-2-3-4 clutch, Allison uses them for its third shift valve and its reverse switch, Ram's RFE gearboxes for the clutch pressure switches in the solenoid block. Ford reports pressure faults under its solenoid codes. P0877 means switch D reports pressure while its clutch is exhausted. GM checks the 1-2-3-4 clutch below 50 kPa commanded and sets it after 5 counts, without MIL. Allison 2007 uses it for the reverse switch reporting R in a forward or park range for over 1 s, type A with MIL; it then suspends the gear ratio checks.
- What you may notice
- Code stored in the gearbox module; on GM without MIL, on Allison with MIL
- Harsh shifts, possibly substitute gear
- Likely causes
- LikelyPressure switch stuck closed or shorted internally
- PossibleSignal wire shorted to ground inside the gearbox
- PossibleClutch circuit does not exhaust: dirt, sticking valve
- RareRange sensor wrong (Allison comparison)
- Repair
- Hard · Usually a job for a workshop.Typical cost: €300 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.