You can see pictures of a similar grommet here:

sunroof-drain-tube-leak-problem-solved-t608588.html

The sunroof drain tube terminates at the firewall behind the steering wheel, to the left. Behind a bunch of wires and stuff in the way. I may find a way to remove it somehow, but I see now way to confidently attach it again.

(BTW, how can I remove the leftmost AC air vent? I removed one screw on the side and I tried prying the vent out but I was afraid too much force would damage something).

Any ideas?

I figured out how to remove driver side vent. Of course there's a visible screw on the left side, remove that. You'll also have to remove the steering wheel cover (under the steering wheel). There are four strong metal clips holding the vent piece, I pushed on the lower right one and pried the vent with a plastic tool, then I pushed the upper right clip and continued prying until the piece was out. I don't think the left metal clips/tabs are easily accessible.

In any case, removing it didn't help that much as there's a huge AC air vent black plastic thingy in the way.

I think I have to unscrew/unclip all wires and everything down there to get a good grip on that drain grommet.

Ideas are still welcome.

Well, I removed the lower instrument panel, all of it. The fuse box, the parking brake and a few things. I didn't want to touch the big white box full of wires I was afraid of breaking the big plastic locks. But I had better access. Not as good as I hoped.

The plastic grommet/fitting the hose connects to on the firewall is covered by the grey undercapet lining. Removing that was very difficult because I would have to remove the pedals and a lot of other things it seems, so I just poked the grommet/fitting hole with a small metal rod and I verified the water flow is good. I could even hear the rod hitting some metal on the other side.

But now the hose is leaking from the top, I think I damaged it when I was trying to clear it from the top with ropes and wires. I will replace the tube in a few days and I will report back.

I'm trying to get the left air vent out of my 2011 Altima SL sedan.

Predictably I broke the stud on the lower left of the trim strip where the mounting screw is, then I removed the horizontal diverter flap assembly.

So you had to remove the cover below the steering wheel and then, from the back, while upside down, pry two clips on the right side of the vent assembly (sort of a box open on both ends) to get it out? Seems like some engineer deliberately made it harder than it has to be, doesn't it? But is that what you had to do?