Need wiring diagram 99' Pontiac Grand Prix SE trunk light

No and correct.

Maybe whatever computer decides whether or not to turn on interior lighting doesnā€™t know whether it is day or night for some reason. Does your car automatically turn on headlights at night?

If your car has a door ajar switch malfunction, the interior lights might remain off until a door is opened.

Yes, it has daytime running lights and they operate as they should.

The time on is limited to 10 min if they are stuck on. As it stands, they shut off in 30 seconds as they should.

New discovery and this made me laughā€¦ sorta.

Thinking that the BCM may be having issues, I went looking for it to grab the number off of it. I found it and also foundā€¦ a GM aftermarket keyless entry system installed. LOL

After unplugging the aftermarket unit, I discovered that the trunk light is still only illuminated when the interior lights are on. Which makes sense seeing as the current BCU doesnā€™t have keyless entry and the only way to trigger the interior lights is by opening a door.

As an aside to the trunk light issue, I wonder if I could swap the BCM for one with keyless entry and have a factory setup. Rock Auto has one for about $130. Not sure itā€™s worth it.

Oh my. With cars being computers on wheels these days, I guess we all have to expect this sort of incompatibility thing cropping up and biting us once in a while.

Hereā€™s a pretty easy, inexpensive option if you can accommodate having to press the button.

Every car has a way to turn on the interior lights. Usually by rotating the dash light dimmer switch. I guess this switch would be one to tie into the supply wire without looking all over the place. As far as ordering a different computer my wife would just tell me to STOP already.