Powertrain, generic · Transmission

P0879 Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent

Check engine lightOn
EmissionsRelevant
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. P0879 reports short dropouts of the D signal. Like P0874 it is documented only for the Corvette C8 dual clutch in GM bulletin 21-NA-033, with MIL: clean the valves, relearn, then trace the circuit if the code returns. No thresholds are published.

Likely causes

Loose contact or corrosion at connector or harness
Dirt or sticking valve (dual clutch)
Sensor or switch with dropouts

Symptoms

  • Warning lamp coming and going
  • Occasional harsh shift or limp mode

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–1,200
Time0.5–4 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

P0875P0876P0877P0878P0874

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.