What is this notch for?

[Ryan]

Hello all

For the life of me I'm unable to find out what this little notch is for that's next to the windscreen (right hand side to the side airbag).

I've taken a screenshot of it as shown by the image below:

I've owned my Citroen DS4 for 6 years and now getting a C4 Grand Picasso and this has the same feature, but nothing I can find in the manual as well as online to hint at what this is for.

Does anyone have any ideas what this is for at all?

Many thanks,

Ryan

[RichardW]

I think it's the ultrasonic sensor for the alarm, or perhaps the mic for the phone.

[wheeler]

If you mean that little bit sticking out the A pillar then yes its the ultrasonic sensor for the alarm, there should be a matching one on the opposite side too.

[GiveMeABreak]

They detect air displacement inside the vehicle. If locking the car with the windows slightly open, you should hold the alarm button down for a few seconds until the led on the button remains on, after switching the ignition off. This will leave the alarm system working but deactivate the internal sensors in the picture as they work on air displacement changes.