What causes a SPN 3302 code?

SPN 3302 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 3302 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3302 active.

How do I fix SPN 3302?

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 3302

SPN 3302 DOC Inlet Pressure Too High

What it means

Indicates excessive backpressure detected at the inlet of the Diesel Oxidation Catalyst (DOC), often caused by internal blockages or downstream flow restrictions.