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: Manifold absolute pressure (map) sensor inspection
Note
Perform the following inspection only when directed.
The following vacuum values are indicated by relative pressure
from the MAP sensor.
1. Connect the SSTs (WDS or equivalent) to the DLC-2.
2. Turn the ignition switch to ON (Engine OFF).
3. Select MAP PID on the SSTs (WDS or equi ...
Mazda 6 Owners Manual: Dtc clearing procedure
1. Start the on-board diagnostic test mode.
2. First press the POWER button, then simultaneously press AUDIO CONT button
for 2 seconds or more.
Caution
Before clearing the DTCs, be sure to enter all of them displayed
in the on-board diagnostic test mode in the Audio Repair Order Form. ...