What causes a SPN 4421 code?

SPN 4421 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 4421 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4421 active.

How do I fix SPN 4421?

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 4421

Detroit DD13/DD15/DD16 SPN 4421

What it means

SPN 4421 - Cylinder #2 Injector Valve Open Circuit. The Engine Control Module (MCM) detects an incomplete circuit or lack of continuity for the fuel injector solenoid on cylinder number 2.