All doors lock automatically when the lock side is pressed. They unlock when the unlock side is pressed.
Driver's door

Front passenger's door

To lock all the doors from an open front door, press the lock side of the door lock switch and then close the door.
NOTE
When locking the doors this way, be careful not to leave the key inside the vehicle.
Locking, Unlocking with Transmitter
Auto Lock/Unlock FunctionMazda 6 Owners Manual: Power brake unit inspection
Warning
The following inspection methods are the simple inspection methods
to judge the function of power brake.
If there is malfunction in power brake unit, replace the power
brake unit as a component.
Power Brake Unit Function Check (Simple Method)
Step 1
1. With the engine stoppe ...
Mazda 6 Owners Manual: Front door key cylinder removal/installation
1. Remove the front door unit.
2. Remove the cover, then remove the bolt.
3. For protector-equipped vehicles, pull out the protector tab from the latch
and remove the protector.
4. Disconnect the rod.
5. Remove the front outer handle.
6. Turn the key cylinder in the direction indicated by ...