I finally got to the bottom of this. It turns off the interior intruder sensors so that you can leave a dog or perhaps a child briefly in the locked car. Procedure is turn off engine, press the roof button, the alarm wRning light now flashes, exit the car, lock it and a loud bleep sounds...
Thanks, I have an account and all else is working OK. The button does nothing. Not lit either.
What is the purpose?
Can you tell me wha page it is in the Manual?