What causes a SPN 624 code?

SPN 624 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 624 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 624 active.

How do I fix SPN 624?

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 624

SPN 624 FMI 2/3/4/5 Common External Lamp Failure

What it means

Indicates a fault in the external lamp circuit or a communication failure between the chassis controller and the lighting system. This code usually points to a short, open, or ground fault in the exterior light wiring.