What causes a P1409 code?

P1409 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 P1409 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1409 active.

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

OBD-II

P1409

Filtered air pressure high fault when greater than APV

What it means

The Engine Control Module (ECM) has detected that the filtered air pressure is higher than the Aftertreatment Purge Valve (APV) pressure, indicating a flow restriction or a valve stuck in the wrong position.