What causes a SPN 594 code?

SPN 594 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 594 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 594 active.

How do I fix SPN 594?

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 594

J1939 SPN 594 — Engine Management parameter

What it means

The SPN 594 indicates a 'General Parameter' error within the Engine Management system, typically signifying that the ECM/MCM has received or is trying to process a parameter that is invalid, out of range, or incompatible with the current software load.