What causes a SPN 386 code?

SPN 386 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 386 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 386 active.

How do I fix SPN 386?

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 386

J1939 SPN 386 — Fuel/Air parameter

What it means

The Engine Control Module (ECM) has detected an irrational signal or circuit fault specifically related to the Air/Fuel ratio parameters, most commonly associated with Intake Manifold Pressure (Boost).