What causes a SPN 333 code?

SPN 333 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 333 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 333 active.

How do I fix SPN 333?

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 333

J1939 SPN 333 — Fuel/Air parameter

What it means

The engine control module (ECM) has detected that the ratio of fuel injected to the air entering the engine is outside of the calibrated operating range.