1. Insert a small screwdriver into the slot and gently pry open the transmitter.

2. Press the portion of the battery indicated by A and remove the battery.

3. Install a new battery (CR2025) into the front portion of the holder with the positive pole (+) facing up. Press on the B portion of the battery to set the battery.
4. Align the front and back covers and snap the transmitter shut.
Battery specification Lithium CR2025 × 1
Note

 Door lock timer unit id code change
Door lock timer unit id code change Transmitter battery inspection
Transmitter battery inspectionMazda 6 Service Manual: Coming Home Light
   The coming home light turns on the headlights (low beams) when the lever is operated.
To turn on the lights
When the lever is pulled with the ignition switched to ACC or OFF, the low beam 
headlights turn on.
The headlights turn off after a certain period of time has elapsed after the 
doors ar ...
   
Mazda 6 Service Manual: Theft-deterrent control module inspection
   1. Remove the theft-deterrent control module without disconnecting the 
connectors.
2. Measure the voltage at the theft-deterrent control module terminals as 
indicated below.
3. Disconnect the theft-deterrent control module connector before inspecting 
for continuity at terminals L, Q, S, T, a ...