It looks like a button but it doesnt look like it does anything at all. What is it and what is it for?

 

I could be wrong but I believe it' just a sensor for the lights(auto day time/night time).

 

Mine has the little glass or plastic "lens" (I guess that's what you'd call it?) still poking out from the speaker grille, but I don't have auto-on headlights, only DRL's, I still have to manually turn on my lights.

 

Someone may have removed the sensor and put a 2.2 k ohm resistor (depending on what year?) to disable the auto headlights.

 

That's probably what happened. 2.2k ohm for 99- and 860 ohm for 98 are the numbers for that

 

Thanks chevyriders! I had the number for mine in my head and knew there was another for the older models but didn't want to misinform.

 

Yea, i accidentally pushed it in a little and it just popped down, her lights stay on almost all the time so the sensor may have been bad anyways.

 

You can remove that speaker grate with a small handled phillips screwdriver. Then you can see what is going on...you can either return it to it's hole, or disconnect and add the resistor like the fellas are talking about on here.

The lights might be on all the time (Auto headlights?) cause it's in darkness under the grate, simulating night time. Just a guess.