1. Remove the VAD check valve (one-way). (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION)
2. Blow through A and verify that air flows from B.
3. Blow through B and verify that air does not flow from A.

Variable air duct (vad) control solenoid valve inspection (l3)
Idle air control (iac) valve inspectionMazda 6 Service Manual: Dtc table
DTCs are common for present and past malfunction diagnosis.
Note
When DTCs not shown in the DTC table are displayed, replace
the SAS unit.
If the air bag system warning light does not illuminate or
remains illuminated when the ignition switch is turned to ON position,
i ...
Mazda 6 Service Manual: Rear crossmember removal/installation
Caution
Performing the following procedures without first removing the ABS
wheel-speed sensor may possibly cause an open circuit in the harness if it
is pulled by mistake. Before performing the following procedures, remove the
ABS wheel-speed sensor (axle side) and fix it to an appropri ...