Can anyone tell me what the little button looking thingy is on the window pillar between the windshield and the driver's side window?

 

Could it be an ultrasonic sensor for the airbag? My S Type has one on the passenger side. More like a vent than a button though.

 

The "thing" is mounted on the window pillar itself and is about the size of a huge beetle. I was guessing that it was either the Nav system microphone, the temperature sensor, or part of the security system (monitoring the inside of the vehicle), or ?. Not a big deal, but I like to understand what things are and what they do.

 

You mean the "thingy" that almost looks like a mini speaker covered with a mesh grill right? There are two more in the passenger area - one on the b-pillar passenger side, and one in the map light overhead console.

These are 3 sensors working together that control your passenger airbag - say if you have a small child in the seat or a passenger that is just sitting way too close to the dashboard for safe airbag operation, this will disable the passenger airbag automatically for safety's sake.

Go ahead and test it out.. I had my girlfriend sitting up close to the dash with a friend in the back seat (gaaaaasp) and the airbag light illuminates on the dash telling me the airbag was disabled. It works on the fly too, I have seen her bending forward to grab her purse off the floor and the light will turn on for a second while she goes digging into that black hole of feminine artifacts!

 

It sounds like you are describing the microphone for the phone system. It's also used for the Jaguar Voice system in XJ's if it is fitted on the car.

The microphone is mounted on the drivers side pillar and looks like a small egg, with two slits in the front.

I guess you could say it also sort of looks like a large beetle...

 

There is a sensor in the seat that turns the airbag off when something in the seat is not of sufficient weight, such as a child. That is the way it is supposed to work...

 

I think that RSCULTHO (Atlanta) may have solved it!
It does look like a small egg...........thanks!

 

Ahh, mine is a 2003 XK8, sorry for the confusion!!

 

I'm glad somebody else asked this question first.

 

Yes, it worked the same way in my 2002 XKR...