What causes a SPN 396 code?

SPN 396 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 396 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 396 active.

How do I fix SPN 396?

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 396

J1939 SPN 396 — Fuel/Air parameter

What it means

SPN 396 indicates an issue with the Fuel/Air Ratio Control (FARC). This signifies the engine controller is unable to balance the fuel delivery relative to the available intake air pressure, often resulting in excessive smoke or power loss.