P08C9: Pressure Control Solenoid M Control Circuit Range/Performance

Meant for a control circuit of pressure control solenoid M that is not open or shorted but behaves implausibly, for instance a coil current that does not follow the command. No manufacturer documents this code publicly. GM, which uses letter M for synchronizer actuation valve 1 of the Corvette dual clutch, publishes only open, low, high and the two hydraulic codes for it; its tables do describe a current check that compares target and estimated current (more than 70 % for 60 ms or more than 400 mA for 300 ms), but without naming P08C9. CARB requires monitoring of transmission solenoids. Possible causes are a coil with drifting resistance, contact resistance or supply voltage problems; shift quality may suffer.

Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

Symptoms

Check engine light on
Uneven shift quality

Most likely causes

Coil resistance out of specification
High contact resistance at connector pins
Unstable supply voltage to the transmission module

What to check, in order

Start with the simplest. You can tick off each step.

Check the fluid level and condition according to the manufacturer
Compare the reading with other engine data while varying the engine speed.
Check the transmission connector
Read the data with a transmission-compatible scanner
Measure the solenoid valve circuit
Leave opening the transmission to a specialized repair shop

Good to know

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P08C9 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
8: Transmission
C9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P08C9?

Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

What causes code P08C9?

The most common causes are: coil resistance out of specification; high contact resistance at connector pins; unstable supply voltage to the transmission module.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.