What causes a P0777 code?

P0777 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 P0777 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0777 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

P0777

Pressure Control Solenoid B Stuck On

What it means

The Transmission Control Module (TCM) has detected that the pressure control solenoid 'B' is stuck in the 'on' position, preventing proper gear ratio changes or clutch application.