What causes a SPN 4406 code?

SPN 4406 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 4406 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4406 active.

How do I fix SPN 4406?

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 4406

Allison transmission code P4406

What it means

Transmission Control Module (TCM) detected an open circuit or electrical failure in the solenoid control circuit (typically related to a specific shift solenoid or valve body component depending on the generation).