What is this air valve called?

Cool, thanks alot, I've got probably 10 connections that leak.. got something g to do on my resets now lol

 

What you are looking at is indeed the passthru. Very easy to replace, very common to leak. None of the brass on it is serviceable. However everyone on the brass fitting below it mounted thru the firewall are. Every Volvo parts department has them, either 1/4" or 3/8". The passthru is marked as to what sensor goes where. There is an old style and a new, both have markings on them just match up the sensor and correct plug and the airlines and you are in business. The electrical plug has an 8mm bolt in the middle accessed from the outside, the inside snaps in.

 

No, those airlines that go into the pass thru go to pressure sensers on the inside, found like any quick connect the o ring inside can be replaced to fix the leak on the smaller lines, but the larger ones require an odd ball size yhat I can't find so I had to buy some fittings and take the blue o ring to transplant into the pass thru

 

What does oo have to do with it? Would like for you to hear the response from my brother, an OP for over 20 years. Lol.