What causes a SPN 794 code?

SPN 794 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 SPN 794 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 794 active.

How do I fix SPN 794?

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

J1939 SPN

SPN 794

J1939 SPN 794 — Engine Management parameter

What it means

SPN 794 indicates an issue with the sensor or communication parameter related to 'Front Axle Speed' as transmitted over the J1939 data link. It typically signifies missing or invalid data from the vehicle speed source (usually the ABS or Transmission ECU).