What causes a P0791 code?

P0791 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 P0791 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0791 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

P0791

Intermediate Shaft Speed Sensor Circuit Fault

What it means

The Transmission Control Module (TCM) has detected a failure or signal loss from the intermediate shaft speed sensor circuit. This sensor monitors the rotational speed of the internal gear set to calculate shifting and torque converter slip.