No. 3 transmitter id code cannot be reprogrammed
Location indexMazda 6 Service Manual: Locking, Unlocking with Auxiliary Key
Turn the auxiliary key toward the front to lock, toward the back to unlock.
To lock
All doors lock automatically when the driver's door is locked using the auxiliary
key.
To unlock
The driver’s door unlocks when the auxiliary key is turned briefly to the unlock
position and then immediatel ...
Mazda 6 Service Manual: Using Automatic Locking Mode (Some models)
Follow these instructions when using a child-restraint system, unless you are
attaching a LATCH-equipped childrestraint system to the rear LATCH lower anchors.
Refer to “Using LATCH Lower Anchor”.
NOTE
Follow the child-restraint system manufacturer's instructions carefully. If
you are no ...