GMC Repair: dash/instrument panel lighting doesnt work, wet repairs, daytime running lights

Question
2002 Chevy Impala LS; 3.8L V6; 76K miles. What would cause the dash/instrument panel lights not to turn on manually with operation of the light switch or automatically when it gets dark (car equipped with daytime running lights - DRL)? About one year ago, the dash lights went out while driving at night and then came back on after an hour or so. The problem occurred again a day or two later for about the same duration. Over time, the problem steadily became worse (occurring more frequently and for longer periods) until, currently, the lights no longer work at all. We have also recently noticed that the back-up lights no longer come on when the door locks and trunk latch are opened with the remote keyless transmitter. Thanks for your help!

Answer
Hi
If the lights do not come on with the by the light switch, and looking at the schematic, I would check a few things.
FIRST I would take it to a good shop in your area, and have the BCM scanned for trouble codes.
It looks like the BCM controls the interior lamp voltages and the back up lamp relay.
Check the DIC/RKE fuse in the passanger side fuse box.
Then if your inclined...
There should be power on the brown white wire going INTO the headlamp switch.
If not the REAR PK LMP fuse in the passanger side fuse box.
If it is hot, the gray wire should be hot coming off the switch.
If not, your switch is faulty.
If so the wire goes into the Left side instrument panel junction block (Located on the drivers side on where you open the door, the end of the dash) That junction block MAY be your fault. If it ever got wet, repairs over on that side..
The more I look at the schematic, the more I see 2 common items for both your faults
1) The BCM
2) The passanger side fuse box
I would go get the BCM scanned, it will set codes for some of these problems.
I Really hope this helps.
Please follow up post anytime.
Good Luck
Pawl