Powertrain, generic · Transmission

P08C4 Pressure Control Solenoid M Performance/Stuck Off

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

GM sets this code on the Corvette's Tremec dual clutch when synchronizer actuation valve 1, the valve for the odd-gear shaft, is hydraulically stuck off. The test runs inside a synchronizer recovery or integrity routine, started after a shift-related fault or when the stored gear does not match the sensed gears at start-up: the shift rods are moved slightly, and if a rod travels 100 µm or less where the valve should move it, a current profile check of the valve has to fail three times before the fault is confirmed. Type A, MIL at once. Bulletin 21-NA-033 blames debris; the fix is GDS valve cleaning three times, service clean and fast learn, and a new control valve body only if it returns.

Likely causes

Valve stuck closed by debris in the control valve body
Debris from a dislodged snap ring in the direct clutch assembly (bulletin 23-NA-197)
Low system pressure or fluid level

Symptoms

  • Check engine light on
  • Odd gears not engaged or engaged late
  • Noise from the transmission area

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–4,000
Time1–6 h

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

Parts involved

pressure control solenoid mvalve body

Related codes

P08C3P08C5P08BBP27B9P27BAP0868

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.