What causes a SPN 7406 code?

SPN 7406 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 7406 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 7406 active.

How do I fix SPN 7406?

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 7406

Cummins fault code 7406

What it means

Aftertreatment 1 Diesel Exhaust Fluid Tank Level/Quality Property Not Supported. This indicates the DEF tank header sensor is sending data that the ECM cannot interpret or the sensor has an internal fault.