Powertrain, generic · Transmission

P0877 Transmission Fluid Pressure Sensor/Switch D Circuit Low

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

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.

Likely causes

Pressure switch stuck closed or shorted internally

Signal wire shorted to ground inside the gearbox

Clutch circuit does not exhaust: dirt, sticking valve

Range sensor wrong (Allison comparison)

Symptoms

Code stored in the gearbox module; on GM without MIL, on Allison with MIL
Harsh shifts, possibly substitute gear

Repair estimate

DifficultyHardWorkshop job

Parts and labour€300–1,500

Time1.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

transmission fluid pressure sensortransmission valve bodytransmission wiringtransmission control module

Related codes

P0875 P0876 P0878 P0872 P0989

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.