I have two situations with my 2001 Yukon.
First, the low beam lights do not come on when dark. They normally come on automatic. Even the switch in truck does not turn them on. The high beams work. Bulbs have been replace, but no help. Low beams do work in early morning hours.
Second problem. This one just started a few weeks ago. When accelerating, the truck makes a sound that is similar to a large grasshopper and cards in the spokes of a bike. Does not happen all the time. It seems to do this more when leaving from work after baking in 100 degree temps all day.
Hope you can help.
Mark
2 separate problems? light problem read this web page it might help…
http://www.nissanforums.com/z31-300zx-t/44258-help-needed-headlamp-sensor-82-280zx.html
Looked for TSB’s for both problems not even a hint for the low beam problem. I would start with bypassing the ambient light sensor in some way (its at the base of the windshield,looks like a little bulb).
For the noise something closer but not exact and that is a roaring noise cause by full engagement of the viscous coupling on the fan (99-07-30-106b) this roar has been common on GM vehicles for quite a while. It doesn’t sound like a grasshopper or like a card in bike spokes but people describe sounds differently. Think of tensioner replacement also if you decide to work with the serpentine belt.
Second thing that comes to mind on the engine noise is a simple serpentine belt noise caused by wear or mis-alignment. GM has a TSB on a belt alignment tool,perhaps this has become a problem for GM. What engine do you have?
GM has come out and stated that its DRL bulbs need replaced by a physically stronger bulb,thats all I could find.