My FAST key took on a mind of its own the other day. For some reason, the security system did not recognize my key as the key I had previously started the car with. None of the keyless systems would work nor would the lock/unlock button work on the remote. When opening the car manually, the car alarm went off. The car would not turn over when I tried just the valet key. After calling my dealer, I learned that I should try starting it by using the back of the key fob to turn the valet key. The lesson learned is that if you ever have a problem you should call your dealer for help. The good news is my other key works. When I have time, I'll get my crazy fast key reprogrammed and find out what the problem was. I just wanted to put this up in case anyone else encounters this problem. I'll keep everyone posted when I get my key fixed.

 

Good to know! Thanks for the helpful post!

 

Finally got my key fixed. They reprogrammed it for free and it works like a gem.

 

the key should probably be replaced. Some early keys were susceptible to issues when in too close proximity to things like cell phones, etc.

newer keys are redesigned.
of course, i have no idea your year, cuz you didnt say.

 

His signature block says "2008 XLS". The keys only had problems with early '07s