Hello again, once i've read this guy's explanation on the key/immo. issue and it clarifies this very well. Quote:
"Each transponder chip has a unique code which is guaranteed to never exist in another transponder. So every single transponder has a different code. To add a key to the car, you put the immobiliser into learning mode and instruct it to accept some keys as valid.
So for example, imagine your car originally had two keys with transponder codes ending 1110 and 6326 (note the real code numbers are actually very long) The cars
(central computer unit) is told to remember these two codes as OK to start the engine. If it see any other codes (or no code) it will not start.
Now you lose one key (1110) and go to the dealer for a new key. He will put the immobiliser into learn mode, clear out all the existing keys and instruct it to read the codes from the original key and the new key he shows it and remember them as valid. Now the immo has two codes stored, the original 6326 and the new one, lets say 8889. You see, the transponder codes themselves can not change, they are built in at the transponder factory. it's the car that is told to remember valid codes and reject invalid ones.
I was trying to say that as far as the car is concerned, when it is put into learn mode it does not care whether the keys are new or second hand. So the answer to your question is yes, a used transponder will be OK since it is the car that needs programming and not the key." End quote.
Hope that helps in any way.