Operation from inside
To lock any door from the inside, press the door-lock knob.
To unlock, pull it outward. This does not operate the other door locks.

NOTE
The red indication can be seen when the door-lock knob is unlocked.

Operation from outside
To lock the rear and front passenger doors with the door-lock knob from the outside, press the door-lock knob to the lock position and close the door (holding the door handle in the open position is not required).This does not operate the other door locks.
This does not operate the other door locks.

NOTE
When locking the door this way:
Auto Lock/Unlock Function
Rear Door Child Safety LocksMazda 6 Owners Manual: Solenoid valve inspection
Resistance Inspection (On-Vehicle Inspection)
Caution
Water or foreign objects entering the connector can cause a poor
connection or corrosion. Be sure not to drop water or foreign objects on the
connector when disconnecting it.
1. Disconnect the negative battery cable.
2. Remove the ...
Mazda 6 Owners Manual: Dtc c1145, c1155, c1165, c1175
Caution
When attaching the tester lead to the DSC HU/CM connector the SST
(49 G066 004) must be used.
Diagnostic procedure
...