What causes a SPN 4557 code?

SPN 4557 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 4557 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4557 active.

How do I fix SPN 4557?

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 4557

Cummins fault code 4557

What it means

Aftertreatment 1 SCR Conversion Efficiency - Low. The engine control module (ECM) has detected that the Selective Catalytic Reduction (SCR) system is not converting NOx emissions effectively.