I have a 2001 Focus with OEM Siemens carkit (from the shape of the holder that has an antenna shape I guess that is for a Siemens C35 , A35, SL45) and I tried with S45, ME45 it did not open the speaker and the microphone, but with S35, A45 it worked well. I changed my mobile with a new Nokia 5140i and I found no one that knows to change just the plug inside the phone holder. In my opinion it just has to know the pins of the Siemens in order to change to the Nokia plug. Every so called "specialist" told me that they can add a new installation, and to remove the existing one. If you know what I mean, the speaker, the microphone, the antenna are nicely fitted from the factory, so, I think it's stupid to replace it. There are just some signals to discover on the old plug to adapt it on the new Nokia plug. Or, it isn't so easy ? My question is if anyone knows the pins from a Siemens and Nokia carkit ?