Ironically, months after this post, I had the interior lights and cluster backlight go out on my truck. Dome lights were not on when unlocking remotely or opening doors, and the backlighting was out after starting the engine and turning the headlight switch on.
Digging through the Workshop Manual, I found that interior dome lights AND backlighting are controlled by the instrument cluster. Backlighting makes sense to me. That's a whole different discussion.
Since my truck has a set of PowerStep running boards that will deploy and retract with the opening and closing of doors, I was able to rule out the Workshop Manual's suggestion that door switches were at fault. Nope, not when the "door open" indicator is illuminated in the cluster.
Chrysler's repair for this is to replace the cluster - no useful troubleshooting in the Workshop Manual. I balked at the idea that the cluster was bad - I don't particularly want to pay for a remanufactured cluster. So I pulled fuse F35 - a 15 amp fuse called "CCN Illumination" - from the TIPM and waited 30 seconds. That reset things and the issue has not come back on my vehicle.
My point is this: if your truck's been working fine and all of a sudden the dome lights and backlighting go out, and you have not made any modifications, pulling the fuse may solve the issue. I made an educated guess, based on a long history of "why was THAT diagnostic test implemented THAT WAY?", that a momentary transient condition can sometimes be enough to trip the diagnostic and turn the output off.
Or think of it this way: the engineers who designed this wanted the $1000 instrument cluster to shut off before anyone could cause problems with it, and failed to tell the service documentation writers that yes, sometimes there are transient conditions that will trip the diagnostic.
