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: Range of topics
This manual contains procedures for performing all required service
operations. The procedures are divided into the following five basic
operations:
Removal/Installation
Disassembly/Assembly
Replacement
Inspection
Adjustment
Simple operations which can be perf ...
Mazda 6 Owners Manual: Vehicle speedometer sensor removal/installation
Without ABS
1. Disconnect the negative battery cable.
2. Remove the battery and battery tray.
3. Remove the air cleaner compornent. (See INTAKE-AIR SYSTEM
REMOVAL/INSTALLATION.)
4. Disconnect the vehicle speedometer sensor connector.
5. Remove the vehicle speedometer sensor.
6. Apply transmi ...