What causes a SPN 520308 code?

SPN 520308 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 520308 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 520308 active.

How do I fix SPN 520308?

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 520308

Injector Cylinder #4 Needle Control Valve, Abnormal Operation (MAX) Cold

What it means

The Engine Control Module (ECM) has detected that the Needle Control Valve for injector #4 is staying open or closed longer than the commanded limit during cold start conditions.