1. Inspect for resistance between the rear door speaker terminals using an ohmmeter.


2. To verify that the rear door speaker outputs sound, apply voltage to the rear door speaker and release using a 1.5-V battery.
Rear door speaker removal/installation
Tweeter removal/installationMazda 6 Service Manual: Mechanical system test
Mechanical System Test Preparation
1. Engage the parking brake and use wheel chocks at the front and rear of the
wheels.
2. Inspect the engine coolant. (See ENGINE COOLANT LEVEL INSPECTION.)
3. Inspect the engine oil. (See ENGINE OIL INSPECTION.)
4. Inspect the ATF levels. (See AUTOMATIC TRANS ...
Mazda 6 Service Manual: Front door speaker removal/installation
1. Disconnect the negative battery cable.
2. Remove the front door trim.
3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
Front Door Speaker Installation Note
Attach the speaker with the wiring harness placed in the groove of the door
unit panel.
...