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: Front door unit removal/installation
1. Remove the front door glass.
2. Remove the inner handle.
3. Remove the front door speaker.
4. Disconnect the power window motor connector, front door lock actuator
connector, power outside mirror connector.
5. Remove the door harness from the front door unit.
6. Remove the bolts.
7. Rem ...
Mazda 6 Owners Manual: Dual proportioning valve replacement (without abs)
1. Remove in the order indicated in the table.
2. Install in the reverse order of removal.
Dual Proportioning Valve Installation Note
Install the dual proportioning valve so that the R mark faces the left side
of the vehicle.
...