How do you program a 2006 Mazda 3 transponder?

To program a transponder key for a 2006 Mazda 3, you typically need two working keys. Insert the first key into the ignition and turn it to the "On" position for about 5 seconds, then turn it off. Remove the key, insert the second key, and repeat the process. If successful, the car's security light will blink, indicating that a new key can be programmed following the same steps. If you don't have two working keys, you'll need to visit a dealership or a locksmith with the proper equipment.