What causes a SPN 4466 code?

SPN 4466 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 4466 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4466 active.

How do I fix SPN 4466?

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 4466

Cummins fault code 4466

What it means

SCR Catalyst Conversion Efficiency Low - Data Valid But Below Normal Operating Range - Moderately Severe Level. The Aftertreatment SCR system efficiency is lower than expected.