I have a 2011 Mazda 6 with Advanced Proximity Keyless Entry. When I bought the car it only had one key and I wanted to have a second key. My first call was to Mazda who wanted over £400 for supplying and programming a key. I then wondered if buying a second hand key was an option but I read many posts on different forums that said the key had to be brand new with an unregistered chip and it wasn't possible to reprogram a key that was already programmed to a different car. This was backed up by the fact that I asked Mazda this exact question and they said the same thing, it would have to be a brand new unregistered key. However I did watch videos on you tube of people programming keys but it was never made clear if these were new or used keys. I have a back ground in computer repairs so I decided I have enough computer knowledge to make it worth while paying £30 - £40 for a second hand key and having a play, if it works I've saved a lot of money and if it doesn't then I've only lost £30. As it happens I had to buy some software as well as the key but I did get it to work. I can say 100% it is possible to reprogram a used advanced proximity key because I've done it, not as cheap as I hoped because of the software but it was a lot cheaper than I was quoted by Mazda. It is possible and I now have the software and am willing to help anyone who needs a key programming for their Mazda, any model. I will charge £20 per key which is massively under what Mazda charge. There are 2 manufactures of these keys, Mitsubishi and Siemens, mine is a Siemens which seem harder to find but they are available if you search. Just make sure you buy the same manufacturer as your original key and the same chip id, you might have to ask the seller for this information, if you pull out the emergency key it's written in small writing behind the key. I can also read all DTC error codes and do other programming but I have to admit I've not tried any other programming yet. If you need any help please message me.