What causes a SPN 3878 code?

SPN 3878 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 3878 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3878 active.

How do I fix SPN 3878?

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.

J1939 SPN

SPN 3878

J1939 SPN 3878 — Body/Chassis parameter

What it means

SPN 3878 indicates a mismatch or communication error regarding Body/Chassis data broadcasted on the J1939 data link. This often refers to specialized equipment parameters like PTO (Power Take-Off) settings or crane/body signals that the engine controller is expecting but not receiving correctly.