Chevrolet Repair: Backlighting goes out for IP, radio, and all HVAC and accy controls, electrical schematics, gm forum

Question
I have a 2001 Chevy Venture Minivan and have an issue with the backlighting going out for the cluster and all of the dash.  When I restart the vehicle and turn the headlights on the backlighting will work fine.  But when I put the van in forward and start to move, the backlighting will turn off.  The gauges and switches all continue to work ok.  I have reviewed some electrical schematics and my guess would be a bad headlamp and IP dimmer switch or the body control module.  Your thoughts?  
Thanks, Scott.

Answer
Hi Scott,
I would normally think a loose ground wire, but that should be random, rather than every time.
It could still be a ground being affected by the shift lever, but that is just a guess.
I would think the IP dimmer would not be affected by shifting.
Does it act the same when shifting into reverse? And you said shift and MOVE. Does it work ok if you shift but don't move?
I will be thinking on this, and get back if I think of anything, but right off hand, it is a puzzle.
There is a good GM forum that is free to join, and loaded with a huge following who will give you some answers. And, it is a very interesting place.

www.chevytalk.org/

Van