What causes a SPN 3812 code?

SPN 3812 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 3812 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3812 active.

How do I fix SPN 3812?

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 3812

J1939 SPN 3812 — Body/Chassis parameter

What it means

SPN 3812 refers to a Body/Chassis parameter conflict or communication failure. It typically indicates that the engine or transmission is receiving an invalid or missing data signal from the body controller regarding a specific chassis-mounted component (like a PTO, crane, or lift).