What causes a SPN 3420 code?

SPN 3420 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 3420 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3420 active.

How do I fix SPN 3420?

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 3420

J1939 SPN 3420 — Body/Chassis parameter

What it means

J1939 SPN 3420: Body/Chassis Parameter. This code indicates that the controller has received an invalid or out-of-range value for a specific parameter related to the body or chassis configuration, typically affecting auxiliary functions or PTO operation.