What causes a P0412 code?

P0412 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 P0412 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0412 active.

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.

OBD-II

P0412

Secondary Air Injection System Switching Valve A Circuit Malfunction

What it means

The Engine Control Module (ECM) has detected an electrical failure or incorrect voltage in the secondary air injection system switching valve control circuit. This system is typically used in specific spark-ignition or specialized vocational engines to reduce emissions during cold starts.