I've had this problem sporadically for the last 2 years but haven't driven the car enough when dark to get to the bottom of the problem. The headlights/parking lights work fine when I manually turn on the headlight switch, but when I leave it on automatic the lights kinda freak out and the parking lights go on but no headlights. Any idea on where I can pinpoint this problem? Is this related to the dreaded BCM failure? Everything else on the car works fine.

 

Most likely the ambient light sensor.

 

That's what I was thinking. I wonder what all is involved to get it replaced/fixed?

 

The sensor is in the front of the dash. If I recall from the time I had my dash completely apart, it's under that front piece that is maybe 3 inches wide, directly behind the windshield. I think to get it "comfortably" removed you need to take the pieces off the pillars (be careful if you do, the way GM did the tabs that hold them in was not moldling them to the pillar, they fused them and I've broken mine and successfully glued them back together). The dash piece lifts straight up (has a bunch of tabs). May want something plastic for a pry tool. The sensor is a small "bubble" like thing and I believe it's near the keyless entry receiver module.

I hope that is the right part and that my description of getting to it helps.

 

Thanks Jason - ya I know where it's located. When I get my stupid keys fixed at the dealership on Saturday I'm going to ask them if this is a common problem and if I can get the part (sensor).