[ivanwang811]

I was buttoning up a few things when I found this small sensor or wire disconnected and I can't figure out what it is. It next to the brake fluid compartment and the cowl. Any guesses?

[relative4]

Hood open/close sensor for the optional security system. The sensor is included on all cars, in case of retrofit I guess.

[Tunafish]

That right there is the auto outside air vent close sensor , i think but havent seen a three hole version... It senses smells/pollution and shuts off the outside air. No clue how it works but thats the idea...
https://www.realoem.com/bmw/enUS/sho...diagId=64_1433

[Emilime75]

The air sensor is on the passenger side, OPs photo looks to be on the driver's side. Assuming LHD.

[Tunafish]

Yeah i was thinking other side.. Weird my hood sensor is just a push switch.

[relative4]

Originally Posted by Tunafish

That right there is the auto outside air vent close sensor , i think but havent seen a three hole version... It senses smells/pollution and shuts off the outside air. No clue how it works but thats the idea...
https://www.realoem.com/bmw/enUS/sho...diagId=64_1433

Wrong.

[Tunafish]

Originally Posted by relative4

Hood open/close sensor for the optional security system. The sensor is included on all cars, in case of retrofit I guess.

Wrong. That is the plug for the hood switch.

[MightyMouseTech]

Originally Posted by Tunafish

Wrong. That is the plug for the hood switch.

Yes, the hood switch for the factory alarm. The car is pre wired for the alarm, but if you don't have the alarm installed it is just the plug sitting there not connected to anything.