Is it possible to use a PID that's already been registered on a car on a different one? 

There was a previous thread that stated the PID records the VIN no. of the car it is first plugged into. However some time ago someone found the file on the PID where it was recorded. I believe they could reset it back so it could be used on another car?

I think it also it depends on if it is the older navigon unit or the newer garmin unit

 

when I did the last major software on our garmin unit I had to re-pair it to the car, so it depends on if you can re-apply the software to in effect factory reset it, and to do that you need to have it registered on fresh to you

I have used my PID in another citigo and it worked fine... I have an Elegance and I used it in a Sport

Ihave the Navigon PID