What causes a SPN 388 code?

SPN 388 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 388 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 388 active.

How do I fix SPN 388?

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 388

J1939 SPN 388 — Fuel/Air parameter

What it means

SPN 388 is a general indicator of a circuit failure in the Fuel or Air parameter sensing system, usually signifying an electrical high/low voltage or out-of-range condition for a specific pressure sensor.