Canadian radio-frequency laws require transmitter signals to “time-out” (or quit) after several seconds of transmission — which may not be long enough for HomeLink to pick up the signal during programming. Similar to this Canadian law, some U.S. gate operators are designed to “time-out” in the same manner.
If you live in Canada or you are having difficulties programming a gate operator by using the “Programming” procedures (regardless of where you live), replace “Programming HomeLink” step 3
with the following:
NOTE
If programming a garage door opener or gate operator, it is advised to unplug the device during the “cycling” process to prevent possible overheating.
Continue to press and hold the HomeLink button while you press and release — every two seconds
(“cycle”) your hand-held transmitter until the frequency signal has successfully been accepted by HomeLink. (The indicator light will flash slowly and then rapidly.) Proceed with “Programming” step 4 to complete.
 Programming the HomeLink System
Programming the HomeLink System Operating the HomeLink System
Operating the HomeLink SystemMazda 6 Owners Manual: Advanced Keyless Entry System
   WARNING
Radio waves from the key may affect medical devices such as pacemakers: 
Before using the key near people who use medical devices, ask the medical device 
manufacturer or your physician if radio waves from the key will affect the device.
The advanced keyless function allows you to lock/u ...
   
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 ...