What causes a SPN 5978 code?

SPN 5978 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 5978 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 5978 active.

How do I fix SPN 5978?

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 5978

Cummins fault code 5978

What it means

Aftertreatment 1 Diesel Exhaust Fluid Pump - Abnormal Update Rate. This code specifically indicates a communication loss or power failure at the DEF pump module.