headlight flicker

The headlights on my wife's 2001 flicker sometimes while she is driving.
What do we check first?

Do they flicker at idle? Do the interior lights (dome and radio) flicker at idle too? if so, there is a revised alternator ground screw that fixes this problem. I just replaced mine, the part costs $5 and takes 5 minutes or so to swap out.
This link explains it and gives part number to order from the dealer. Use a magnetic screw driver to replace this as you will be doing it blind (its kinda up under the cowl on the backside of the motor). Its OK if you drop the original when removing, but if you lose the new one with washer it'll fall back on the motor and get lost (the washer is the most IMPORTANT part).
Hope this helps!
http://www.impalahq.com/TSB/TSB01-06-03-005.html

The new screw took care of our vans flickering as well.

Keith

Can you help with the exact location of this grounding screw? I have looked over, under, and around and can't seem to locate it. What is it next to? alternator, plug wires, transmission? please help.

The screw is located on the back of the alternator under a plastic cover. It is hard to see to do the job, so you kind of have to "feel around" to be able to get it done.
In the future please check the dates of the posts and avoid posting in outdated threads. you can start a new thread and link to the old one.