What causes a SPN 3985 code?

SPN 3985 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 3985 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3985 active.

How do I fix SPN 3985?

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 3985

J1939 SPN 3985 — Body/Chassis parameter

What it means

SAE J1939 Body/Chassis Parameter - This code generally indicates a configuration error, data out of range, or a communication fault for a specific parameter defined by the body controller.