What causes a SPN 2904 code?

SPN 2904 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 2904 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2904 active.

How do I fix SPN 2904?

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 2904

J1939 SPN 2904 — Aftertreatment/Emissions parameter

What it means

Aftertreatment 1 Intake Oxygen 1. Indicates that the measured oxygen levels in the exhaust stream at the intake of the aftertreatment system are outside of the expected range, potentially signaling an efficiency or combustion issue.