With Audio Unit

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Switch the ignition to ACC or ON.
Turn the audio unit power to ON.
Press the AUDIO CONT switch.

Fig 1: Identifying AUDIO CONT Switch
Courtesy of MAZDA MOTORS CORP.
Select "Welcome ON" or "Welcome OFF".
Press the AUDIO CONT switch.

Fig 2: Screen Display - Without Bose® And With Bose®
Courtesy of MAZDA MOTORS CORP.
Select "ON" or "OFF".

Fig 3: Pushing AUDIO CONT TUNE
Courtesy of MAZDA MOTORS CORP.