What causes a SPN 804 code?

SPN 804 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 804 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 804 active.

How do I fix SPN 804?

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 804

J1939 SPN 804 — Engine Management parameter

What it means

SPN 804 typically refers to Engine Management Parameter configuration or communication issues over the J1939 data link, often indicating the ECM cannot receive or synchronize specific engine management settings.