What causes a SPN 591 code?

SPN 591 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 591 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 591 active.

How do I fix SPN 591?

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 591

J1939 SPN 591 — Engine Management parameter

What it means

SPN 591 indicates a 'Faulty Parameter' or 'Programming Error' within the Engine Management system. Essentially, the ECM is receiving or hosting data that doesn't match its expected configuration.