What causes a SPN 789 code?

SPN 789 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 789 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 789 active.

How do I fix SPN 789?

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 789

J1939 SPN 789 — Engine Management parameter

What it means

SPN 789 indicates a fault with the Wheel Speed Sensor for the ABS system, specifically the Front Axle (Left Side). It relates to signal irrationality or circuit failure.