What causes a SPN 354 code?

SPN 354 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 354 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 354 active.

How do I fix SPN 354?

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 354

J1939 SPN 354 — Fuel/Air parameter

What it means

Relative Humidity sensor signal is out of range, erratic, or invalid. This sensor helps the ECM calculate NOx emissions and manage EGR flow.