Well, I learn something new every day thanks Rick.
Andy
The code is set from the manufacturing plant and is the last 3 or 4 (can't remember exactly) numbers of the VIN number. Hopefully, no previous owner has changed it.
By default, there is no code set, someone has to enable it in the stereo settings, and at that point the code can be set to any code. If the code is enabled, there is no harm in trying the last 4 numbers of the vin code. Either way, if it doesn't display SEC when the stereo is switched on, there is no code set.