What causes a SPN 340 code?

SPN 340 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 340 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 340 active.

How do I fix SPN 340?

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 340

J1939 SPN 340 — Fuel/Air parameter

What it means

SPN 340 indicates a Fuel/Air Parameter error, specifically identifying a discrepancy or out-of-range value regarding the engine's air intake or fuel temperature data used for combustion calculations.