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P0412: Secondary Air Injection System Switching Valve A Circuit

Severity: Low If the light is steady and the engine runs normally, schedule diagnosis. Stop for smoke, a burning electrical smell, or severe rough running; those are not normal secondary-air symptoms.

What does P0412 mean?

The circuit operating secondary-air switching valve A has a fault. This is a valve-control electrical diagnosis, not simply evidence that too little air reached the exhaust.

Generic OBD-II definition: Secondary Air Injection System Switching Valve A Circuit. Confirm applicability in your vehicle service information.

Common causes

  • Open or shorted switching-valve wiring
  • Failed valve-control solenoid
  • Lost solenoid feed or poor connector

Symptoms

  • Check engine light
  • Increased cold-start emissions
  • Often normal driving

Diagnostic focus

Do not replace the pump just because the system uses one. A working pump cannot deliver air correctly if the switching valve is never electrically operated.

Can I keep driving with P0412?

Severity: Low If the light is steady and the engine runs normally, schedule diagnosis. Stop for smoke, a burning electrical smell, or severe rough running; those are not normal secondary-air symptoms.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

  • Locate switching valve A from the system diagram
  • Test its power, control circuit, and winding
  • Verify commanded valve operation after repair

Related codes

P0410
Secondary Air Injection System MalfunctionP0411
Secondary Air Injection System Incorrect Flow DetectedP0418
Secondary Air Injection System Relay A Circuit

Sources & review

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.