What causes a SPN 6636 code?

SPN 6636 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 6636 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6636 active.

How do I fix SPN 6636?

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 6636

Cummins fault code 6636

What it means

Aftertreatment 1 Hydrocarbon Dosier - Injector Performance/Clogged Injector. The ECM has detected that the aftertreatment fuel injector is not delivering the expected amount of fuel for DPF regeneration.