What causes a SPN 326 code?

SPN 326 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 326 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 326 active.

How do I fix SPN 326?

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 326

J1939 SPN 326 — Fuel/Air parameter

What it means

The engine ECM has detected a significant mismatch between the commanded fuel delivery and the measured air intake, indicating that the air/fuel ratio is outside of the programmable operating limits for safe combustion.