What causes a SPN 4039 code?

SPN 4039 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 4039 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4039 active.

How do I fix SPN 4039?

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 4039

Cummins fault code 4039

What it means

Aftertreatment 1 DEF Tank Heater Control Unit - Abnormal Update Rate. This indicates a loss of communication between the Engine Control Module (ECM) and the DEF tank heater controller over the J1939 data link.