What causes a SPN 520305 code?

SPN 520305 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 520305 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 520305 active.

How do I fix SPN 520305?

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 520305

Injector Cylinder #1 Needle Control Valve, Abnormal Operation (MAX) Cold

What it means

The MCM has detected that the Needle Control Valve for Injector #1 is taking too long to close or reach its commanded position specifically during cold operating conditions.