These locks are intended to help prevent children from accidentally opening the rear doors. Use them on both rear doors whenever a child rides in the rear seat of the vehicle.
If you slide the child safety lock to the lock position before closing that door, the door cannot be opened from the inside. The door can only be opened by pulling the outside handle.

Locking, Unlocking with Door- Lock Knob
Trunk LidMazda 6 Owners Manual: Knock sensor inspection
Note
Perform the following test only when directed.
Resistance Inspection
1. Turn the ignition switch to LOCK.
2. Disconnect the knock sensor connector.
3. Measure the resistance between the knock sensor terminals A and B using an
ohmmeter.
If not as specified, replace the knock sens ...
Mazda 6 Owners Manual: Front seat removal/installation
Warning
Handling the front seat (side air bag) improperly can accidentally
deploy the side air bag, which may seriously injure you. Read AIR BAG SYSTEM
SERVICE WARNINGS before handling the front seat. (See SERVICE WARNINGS.)
1. Turn the ignition switch to the LOCK position.
2. Disconne ...