What causes a P0799 code?

P0799 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P0799 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0799 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

P0799

Pressure Control Solenoid C Intermittent Fault

What it means

The Transmission Control Module (TCM) has detected an irregular signal or intermittent electrical failure in the circuit for pressure control solenoid C. This affects the hydraulic fluid pressure required for smooth gear engagement and shifting.