What causes a SPN 339 code?

SPN 339 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 339 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 339 active.

How do I fix SPN 339?

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 339

J1939 SPN 339 — Fuel/Air parameter

What it means

Fuel/Air parameter SPN 339 often specifically refers to "Water in Fuel" or fuel density/quality issues depending on the OEM implementation (often paired with FMI 0-4).