No. 3 transmitter id code cannot be reprogrammed
Location indexMazda 6 Service Manual: Automatic transaxle fluid (atf) replacement
Warning
When the transaxle and ATF are hot, they can badly burn you. Turn
off the engine and wait until they are cool before changing the ATF.
1. Remove the oil dipstick.
2. Remove the oil drain plug and washer.
3. Drain the ATF into a container.
4. Install a new washer and the drain ...
Mazda 6 Service Manual: Scheduled Maintenance (U.S.A., Canada, and Puerto Rico)
Follow Schedule 1 if the vehicle is operated mainly where none of the following
conditions (severe driving conditions) apply.
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
...