What causes a SPN 6629 code?

SPN 6629 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 6629 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6629 active.

How do I fix SPN 6629?

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 6629

Cummins fault code 6629

What it means

Diesel Particulate Filter (DPF) Efficiency - Out of Calibration. The ECM has detected that the DPF is no longer effectively capturing soot, often via the Particulate Matter (PM) sensor.