What causes a SPN 239 code?

SPN 239 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 239 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 239 active.

How do I fix SPN 239?

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 239

J1939 SPN 239 — Fuel/Air parameter

What it means

Fuel Rack Position. Monitors the mechanical position of the fuel injection pump rack, typically found on older electronic-over-mechanical systems.