What causes a SPN 3479 code?

SPN 3479 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 3479 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3479 active.

How do I fix SPN 3479?

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 3479

Aftertreatment Fuel Pressure Control Unit Leakage

What it means

The Engine Control Module (ECM) has detected that the aftertreatment fuel injector or hydrocarbon doser is leaking fuel into the exhaust when it should be closed.