Powertrain, generic · Transmission

P08C5 Pressure Control Solenoid M Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

GM uses this code on the Corvette's Tremec dual clutch when synchronizer actuation valve 1, serving the odd-gear shaft, keeps pressure on although it is commanded off. The check runs whenever the selector pilot valve changes position: a valve stuck on keeps pushing a shift rod, so after the switch the pressure is routed elsewhere. If within 200 ms one rod moves unintentionally by 1000 µm or more while another relaxes by 125 µm or more, and both position sensors are electrically fine, the fault is set. Type A, monitored continuously. Bulletins 21-NA-033 and 23-NA-197 list it with the other valve codes; debris in the control valve body is the main cause. P08C4 is the stuck off counterpart.

Likely causes

Valve held open by debris in the control valve body
Debris from a dislodged snap ring in the direct clutch assembly (bulletin 23-NA-197)
Worn valve bore in the control valve body

Symptoms

  • Check engine light on
  • Clunks or unwanted gear engagement on the odd shaft
  • 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

P08C3P08C4P08BCP27BAP27B9P0869

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