So I lost another mustang key and down to just one. I programmed a few more and while I was at it, I wanted to program keyless entry as well. I put the car into program mode by putting the key into the ignition and turning it from off to on 8 times, leaving it in the on position on the last turn and the doors cycled. I have to fob's that I want programmed that are both aftermarket. One is the standard one and the either is the switch key style and lights up when you press any of the keys. Neither of them would program to my car. I know it isn't faulty batteries as I can see the switch key style one light up once pressed. I did some research and I found that some people solved this problem by pulling the radio fuse in the BEC fuse box underneath the hood due to interference. I tried that and neither of my keys would program. I truly believe it has something to do with my car's receiver because I've read reviews about both of these fob's and have seen people program the exact same ones with the exact same year/make/model as my mustang. If anyone has any suggestions, I'd greatly appreciate it as I'm not too automotive savvy yet.

 

Have you considered looking for an OEM remote? Probably would eliminate your issue.