C5 II Remote locking does not work

[Lale]

My account has just been activated so I can add my experience.
I have C5 HDI 2L MY2006 which I bought recently with the only one key which did not work for remote locking. Opened key and found PC board heavily damaged probably by Coca Cola (printed circuit disintegrated). As I was reading your treads concluded that if I buy on e-bay another key and transfer PC to my key I will be able to resync. Did this forum's recommended procedure with no success. Went to Locksmith, he checked that my key transmits, connected diagnostic machine and used code which I have and everything looked OK. He thinks that is something wrong on receiving side.
Is it possible that resync did not work and key transmits previous code?
Any experience with checking receiving path?
I have portable oscilloscope and could check if the signal has been received if I know which connector on CAM or BSI to look at.
Thanks

[myglaren]

Second hand keys have been found not to work with C5s. They appear to be once-only programmable.

[GiveMeABreak]

Lale - you have to be careful when re-programming the keys to make sure you code BOTH the keys together. When using the Lexia / Diagbox to code the keys you have to tell it how many keys the customer has in total and they both need to be done regardless. When I had some work done, the Garage lost my vehicle configuration options when using the diagnostic kit (although thankfully they made a printed copy of all the screens beforehand) so were able to restore the data. However, this needed my keys recoding. When they coded the one key I was using - all was fine until I picked up the spare set one day and of course it wouldn't open the doors or start the car. The technician realised what had happened and I had to go back and get BOTH keys recoded again - you can't just do one as it disables the other one.

Mine is an X7, so as Myglaren says, there could be differences with the Mk1 & Facelift models.