If the OBC is the full version with the key in position 1 you press ‘CODE’ followed by a number combination of your choice (using the number buttons used to set the clock - up to four characters I tink) then ‘CODE’ again then switch off. The red LED will remain lit indicating it is locked.

To disarm is the same process is followed. If you try to start without disarming the ignition will be dead, the ‘gong’ goes and the OBC just flashes up a warning.

You can use a different code every time you arm it if you want but it means you’ve got to remember it

Sounds like a ball ache but its actually dead easy and quick if you use a simple code that’s quick to enter.

WD