What causes a P1039 code?

P1039 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 P1039 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1039 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

P1039

DOCP Doc pressure too high fault

What it means

Diesel Oxidation Catalyst (DOC) Inlet Pressure Too High. This indicates the engine control module (ECM) detects backpressure exceeding the maximum allowable threshold at the DOC inlet.