I have a 2002 monte carlo ss. i bought it used and it has no interior or dome lites. I replaced the dome lite with a new bulb and checked the fuses. when i open the door the message center tells me the doors ajar but no dome lite. as far as i know there is no relay. could it be the dimmer switch? if so how could i test the old one, because a new one is over $100.00.
The dimmer control is only for the dash lights. There may be a light control module that the door switches tie to and controls the light and if so, there may be a problem with it.
Pick-ups have a “dome overide” just a thought about your Monte.
Have you done a “walk-around” to check exterior lights? Maybe your interior lights are trying to tell you something.