What causes a SPN 2891 code?

SPN 2891 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 2891 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2891 active.

How do I fix SPN 2891?

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 2891

J1939 SPN 2891 — Aftertreatment/Emissions parameter

What it means

Aftertreatment 1 Intake Dew Point. This code indicates that the aftertreatment system cannot accurately determine if condensation is present in the exhaust, preventing the activation of NOx sensors to protect them from thermal shock.