P08C4 code meaning
Pressure Control Solenoid M Performance/Stuck Off
Powertrain system Generic code P08xx codes Check engine light
What P08C4 means
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.
P08C4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P08C4
- Check engine light on
- Odd gears not engaged or engaged late
- Noise from the transmission area
Common causes of P08C4
- Most likelyValve stuck closed by debris in the control valve body
- PossibleDebris from a dislodged snap ring in the direct clutch assembly (bulletin 23-NA-197)
- Less likelyLow system pressure or fluid level
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Pressure control solenoid mValve body
What each part of P08C4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 8 | Area: transmission. |
| C4 | The exact fault in that area. |
What to do next
- Note P08C4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P08C4
What does P08C4 mean?
P08C4 means "Pressure Control Solenoid M Performance/Stuck Off". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P08C4?
Drive gently and only to a workshop. With P08C4 the car can go into limp mode (reduced power) to protect itself.
Will P08C4 fail an emissions test?
Yes, it can. P08C4 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P08C4 to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P08C4 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.