What causes a SPN 979 code?

SPN 979 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 979 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 979 active.

How do I fix SPN 979?

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 979

J1939 SPN 979 — Engine Management parameter

What it means

SPN 979 typically relates to a memory or software parameter error within the Engine Management System, specifically often indicating an 'Engine Control Module Data Error' or 'Implementation Memory' fault.