https://www.quora.com/How-do-automatic-headlights-work Probably similiar to this. Photo eye may be dirty or in bypass mode, light sensitive of coarse.

 

 

My photo eye is on the dash I believe but controls all lights on or off pending on dark conditions. Setting through light switch itself. HUD display control to right of lamp control (heads up display, like fighter aircraft use; windshield projection).

Manually switch beams and I don't think it has auto dim per factory manual, maybe. Recall better GM cars had those back to the 50's even but we're always switching with any light source photo eye would detect.

Example also is our lights always come on when car's in garage even on sunny day. After car is backed out of garage lights will shut off when eye detects the sun.

I mean I just read what the M/S was for on the shift selector (manual/sport). '16 LaCrosse a sports car? I think not, other one might be.

 

that's what happened to my photo sensor awhile back, was covered in dust and couldn't see. just a simple clean fix did the trick.