Variable Air Duct (VAD) Check Valve (One-Way) Inspection

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Remove the VAD check valve (one-way). (See INTAKE AIR SYSTEM REMOVAL/INSTALLATION .)
Blow through A and verify that air flows from B.
Blow through B and verify that air does not flow from A.
- If not as specified, replace the VAD check valve (one-way)
  
  Fig 1: Identifying Variable Air Duct (VAD) Check Valve
  Courtesy of MAZDA MOTORS CORP.