What causes a SPN 393 code?

SPN 393 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 393 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 393 active.

How do I fix SPN 393?

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 393

J1939 SPN 393 — Fuel/Air parameter

What it means

SPN 393 indicates a communication or data validity error regarding the Fuel/Air Ratio parameter transmitted over the J1939 network.