What causes a SPN 378 code?

SPN 378 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 378 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 378 active.

How do I fix SPN 378?

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

Log in Sign up

J1939 SPN

SPN 378

J1939 SPN 378 — Fuel/Air parameter

What it means

Circuit fault related to the Fuel Injection Pump Fuel Control Valve (commonly found on CAPS or VP44 fuel systems).

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free