Your radio display and odometer should not be so dim during the day that you either have difficulty seeing the digits or notice they are dimmed. I will say however, that after looking at the schematics, it is difficult to see how two separate and independent class 2 communication dimming control circuits ( one for radio, one for odometer) are acting in the same manner. It sounds like a problem with the BCM itself. The next logical first step would be to get it scanned with a Tech 2 for any Body error codes and see if that points you towards a solid solution.