Central locking button missing

[myo]

Our Lingo Mk2 came with remote central locking, but, having fixed the rear lock, and judging by the missing button on the dash (it just has a fake blanking button) I'm assuming it was retro fitted when the alarm was installed by the previous owner. (I can't ask as it came to me via a dealer)
Does anyone know if I can add the dash lock b0tton so we can lock/unlock the doors internally? I'm not sure if the van is pre-wired for the motors or if new cables have been run into the doors as I've only looked at the tailgate so far. If the original wirng was used can I assume it's been tied into the ecu to control it?

[steve valentine]

Mine is retrofitted. I just press the button on the remote when I'm in the van.

[myo]

I would do that but it'll arm the alarm, which will then go off if I open the door.

[addo]

Pull out the blank, to see if the plug is behind. You could also strip the trim off one door and see if the latch is original or modified.

[steve valentine]

I would do that but it'll arm the alarm, which will then go off if I open the door.

Mine arms it only when the engine isn't running.

Have you tried it with the engine running and the doors closed?