I have had 2 Chevy trucks and both had non functional dome lights. This new one also had a dead dome and bed light. In utter fustration I pulled out the rearseat and started tracing wires.
Found the ground was not making it to the interior light control module. Had good power.
Made it to the driver side wire channel and found two plugs under the carpet right behind the driver seat next to the door pillar. I had to remove the plastic trim to find them. They were badly corroded and in need of replacement. They branch off of the main body harness. The dome wires run up the driver door pillar and the bed light runs back through the wire channel and up the rear cab right by the left rear speaker and across.
I wanted to be detailed about this fix as is has presented itself a few times to me and to others.

This is on my 1998 Chevy k3500 crew cab dually

Now to pull the rest of the interior and replace the carpet!
George