What causes a SPN 3774 code?

SPN 3774 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 3774 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3774 active.

How do I fix SPN 3774?

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 3774

J1939 SPN 3774 — Body/Chassis parameter

What it means

Body/Chassis Specific Parameter. This code typically indicates an issue with the configuration or data signal of a specific chassis-mounted component, often related to auxiliary body equipment, PTO, or lift-axle parameters.