What causes a SPN 3946 code?

SPN 3946 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 3946 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3946 active.

How do I fix SPN 3946?

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 3946

J1939 SPN 3946 — Body/Chassis parameter

What it means

SPN 3946: Engine Configuration Data Error / Body Controller Parameter Mismatch. This code indicates that the Engine Control Module (ECM) and the Body Control Module (BCM/VECU) have conflicting configuration data or an invalid parameter set for a specific vehicle feature.