Powertrain, generic · Transmission

P0874 Transmission Fluid Pressure Sensor/Switch C 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. P0874 reports short dropouts or flutter of the C signal without a lasting low or high. It is documented only in GM bulletin 21-NA-033 for the Corvette C8 dual clutch, with MIL: dirt and sticking valves are cleaned, the clutches relearned, and only then the circuit traced. Thresholds are not published.

Likely causes

Loose contact or corrosion at connector or harness
Dirt or sticking valve (dual clutch)
Sensor or switch with dropouts
Low fluid level, pressure drops in corners

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

P0870P0871P0872P0873P0879

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