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 Passenger Occupant Classification Sensor
Your vehicle is equipped with a front passenger occupant classification sensor
as a part of the supplemental restraint system. This sensor is equipped in the front
passenger's seat cushion. This sensor measures the electrostatic capacity of the
front passenger's seat. The SAS unit is designed ...
Mazda 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 ...