Courtesy lights? Not so much

[pricetag2]

I recently purchased a 2002 base Deville. 100,000 miles and in very nice condition. But the courtesy/entry illumination lights don't work. If you push the manual buttons, the rear and reading lights work. The dash dimmer switch will not turn them on, doors opening won't turn them on. I pulled the DTC codes but nothing stands out. Is this a RIM or IPM or communication problem? I'm asking before I take it to a (gulp) dealer.

Thanks

[Texas Jim]

Have you checked all of the fuses for the courtesy lights?