What causes a SPN 3947 code?

SPN 3947 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 3947 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3947 active.

How do I fix SPN 3947?

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 3947

J1939 SPN 3947 — Body/Chassis parameter

What it means

SPN 3947 indicates a communication fault or parameter mismatch related to the J1939 Body/Chassis interface. It usually signifies that the ECM is missing expected data from a body controller or that the body configuration parameters are invalid.