Believe it or not, it's probably the ignition switch.
I fixed these same issues on my '02 GTP.
My HVAC controls, DRL, DIC, HUD all were acting flaky.
The ignition switch had to be replaced.
I tried the ignition bypass first, hoping to save the cost and effort of replacing the switch assembly, but the bypass only worked for a few start cycles. The ignition switch contacts were badly scorched/burned.
This is an attachment you can download that describes how to do the bypass. It inserts a relay in the ignition circuit to prevent the high-current flows through the switch contacts. (
http://www.grandprixforums.net/attac...-bypasspnp.pdf),
Use this diagnostic process to verify that it is the switch:
http://www.sparkys-answers.com/2009/...-changing.html When I checked mine, I found 0 volts at the HVAC/DIC fuse.
Excellent write-up on switch replacement procedure here:
http://www.sparkys-answers.com/2009/...-changing.html
The best, bullet-proof solution would be to replace the switch AND install the bypass with the new switch. If you do this, the new switch will never see the high current loads and it should last indefinitely.
Switches are available from any auto supply. I actually got the best price on a Delco unit. Good luck!
Joe