What causes a SPN 278 code?

SPN 278 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 278 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 278 active.

How do I fix SPN 278?

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 278

J1939 SPN 278 — Fuel/Air parameter

What it means

SPN 278 indicates a mismatch or range/performance issue within the Fuel/Air control parameters, specifically relating to how the engine calculates air density and turbocharger efficiency.