What causes a SPN 3225 code?

SPN 3225 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 3225 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3225 active.

How do I fix SPN 3225?

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 3225

SPN 3225 — Aftertreatment 1 Outlet NOx

What it means

Aftertreatment 1 Outlet NOx sensor - Abnormal update rate, voltage, or rationality fault. This indicates the engine control module (ECM) is detecting incorrect data or a lack of communication from the NOx sensor located after the SCR catalyst.