Hi there,
I've been lurking here for some time now and finely have a question/ problem that I can't find and answer for. I have a 2004 LB7 and the high beams will not come on with the MFS pushed forward, however they will come on w/ the low beams when the stalk is pulled back. Could this be a bad MFS or is there something else that I may be overlooking. Any help or guidance that anyone may provide will bee greatly appreciated. Thanks.

The headlamp relays (one for low and one for high) are both controlled by the BCM which receives the input from the MFS. Would really need to see if the BCM is receiving the input from the MFS. Or you may just try swaping the hi and low relay and see if the problem changes with the relay. Both relays are located in the underhood fuse block

Thanks for the fast reply. That was the first thing I tried as I have had a relay problem on another truck. Is there any way that I can check to see if the BCM is rec input from the MFS. By the way, what part of Baltimore are you from and do you work for a dealer there, I'm in southern A.A. county.

I am close to Towson, Work at Fox Chevrolet in Timonium.

Well you can try this, I have never done it, but looking at the schematic, you can give it a try, should work

Do you know where the BCM is?

If so

look for the brown connector on the BCM, find pin B9, will be a lt grn wire, when turning the high beams on (will not work pulling back on the stock for the flash to pass, must be pushed forward turning on the high beams) When the high beam is turned on, this wire should be grounded.

I know where the BCM is. I'll try to check the ground tommorow. If there is no ground would that indicate a bad switch? Thanks for your replies.

If the wire does not ground when putting the switch on high beam, its either a switch or a wire

The wire did not ground with the stalk forward. When I grounded the connection @ the BCM the lights worked. I also traced the wire as far as I could and found no break/ short, so should I assume a bad MFS? At $150.00 I'm trying to be as sure as possible. Again thanks for all of your help.

Go to the bottom of the column where the wires come out for the mfs, ground it out there and see if the lights work, if they do, then its either in the short amount or in the column or the switch.

Of course if you really wanted to do it cheap, just wire in a switch hooked to a ground

Thanks, I'll buy the MFS and see if that works. Thanks again.

np

I replaced the MFS and still did not get high beams in the forward position however I still had them in "flash" position. That was yesterday. Now I don't have them at all.
I checked continuity between the Lt. Green wire @ the MFS and B9 on the BCM and it shows open, is that correct, if so do you have any other ideas. Thanks

I will try and take a look tomorrow see if there is anything else.

Here is the schematic

http://service.gm.com/engif/000/001/247/1247982.gif

Thanks for the help. I found a couple of broken wires down the column. They were behind the factory electric tape and man were they thin. Again, thanks for your assistance.

No problem, glad you found it.