Review on High-Quality Car Key Fob Keyless Entry Remote for Mazda 6 2003-2005 Models (KPU41805, 41805, 4238A-12076) by Adam Ross

The key fob syncs with the car the first time. Programming for a 2004 Mazda 6 was as simple as leaving the driver's door open, inserting the key, and turning the ignition on three times in 10 seconds. Leave the key and close and open the driver's door three times. When the door is opened for the third time, the machine will click the locks and say it's ready to be paired. Press a few buttons on each key fob to open the door locks and show they're in sync. Remove the key and you're done. Took a maximum of 1 minute