What causes a SPN 3604 code?

SPN 3604 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 3604 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3604 active.

How do I fix SPN 3604?

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 3604

J1939 SPN 3604 — Body/Chassis parameter

What it means

SPN 3604 typically refers to an Auxiliary Digital Output circuit driver fault. This relates to electrical signal outputs from the vehicle chassis controller to body equipment.