What causes a SPN 3771 code?

SPN 3771 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 3771 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3771 active.

How do I fix SPN 3771?

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 3771

J1939 SPN 3771 — Body/Chassis parameter

What it means

SPN 3771 usually refers to a 'Body/Chassis Parameter' error, often specifically related to the Engine Shutdown Switch or a specific auxiliary PTO input communicated over the J1939 datalink that is outside of the expected range or missing.