There are two possiblities:1) the dome light switch is on(usually part of the instrument light dimmer control)2) door ajar switch is bad. Does the door open warning come on while driving? If so, you probably have a bad switch, they tend to stick and give the false warnings, it has been a fairly common problem. Good luck
I have checked the wiring schematic for this vehicle system and there are a couple of things to check. I am assuming, that the dome lights go out on their own when the Bussed Electrical Center (BEC) times out and terminates the power feed to the lights to prevent a dead battery. The schematic shows the BEC supplying power to a Smart Junction Box (SJB), the SJB is connected to the illumination dimmer switch and the overhead console (the light assembly). There is a violet /yellow wire that supplies a ground to the SJB when the dome lights are requested. Then there is a Black/ Light blue wire from the SJB to the light assembly and that provides power (B+) to the light assembly. the switches at the light assembly provide the ground to light the lights. By what I see, to have the dome lights on all the time you have to have power at the black/light blue wire at all times and bad switches (there are two) in the dome light assembly providing ground at all times, even though the switches are in the off position.