I just purchased a 2004 S500 that came with 2 nec type keys. One works perfectly. The second one would only work the doors and not unlock the ignition to start the car. The seller said it was that way when he bought the car. Today I took the electronics out of the case and made sure the case was clean and the optics were not being blocked. When I was testing the cleaned fob I found it remained the way it had been, not letting you turn the fob, but I then pushed the door unlock button and that opened the key module and the fob turned and started the car. I found that you can press any of the 4 buttons and then turn ignition on. Anyone know anything about this? Is there a feature in the security system that would require this extra action or do I just have a weird key fob?