2001 Impala Headlights

I am trying to wire my headlights so that all four lights are on when the high beams are on.  I have done this with other vehicles with a simple relay to using the high beam as the signal with the output to the low beam.  However, my Impala has the high beam daytime running lights AND I have discovered that the headlights seem to work by ground switching, meanging, that there is constant voltage in the wires going to the headlights.  How can I accomplish what I am trying to do?  Do I have to wire this up under the dash instead of under the hood?  Help please.

Well I've never done this application personally...but I would wire it under the dash just to be safe from water,dust, humidity..things of that nature. Those things can really hurt a light circuit...(Well not all of them...just the water if it touches the bare wire.)~The Rookie~

Rookie of the year that is...

Don't let the smoke out of your equiptment..it doesn't go back in.

you have to add a diode in-line with the parking lights otherwise the service engine soon light will come on. so based soley on that I wouldn't try it.

Can someone tell be the color of the wires coming from the high/low beam switch?  If I pull the high/low beam switch halfway back, I get all four headlights on at the same time.  I was hoping someone can tell me so I don't have to probe a lot of wires to see which ones are the high and low beam wires coming from the steering column.

im pretty sure Painless Wiring sells a GM harness that will do the same thing you are trying to do.

I know about their kits however you can buy the same thing from your local parts store.  All you need is a relay, wiring, connectors, and an in-line fuse.  They have a specific kit for the GM truck line but I already have my truck wired with the above mentioned parts.  The problem with my Impala is that the headlights have constant voltage to them and it isn't as simple as using the high beam to trigger the relay and send power to the low beam.