the interior lights (map lights) in the rearview mirror suddenly refuse to shut off, i've unplugged the lighting module from the mirror after trying ever other possible fix.
i made sure all doors are tightly closed, on/off buttons do nothing, dimmer for cabin lights is down, i have gone thru all the common sense possibilities.
i read this could be the LCM but chances are it is likely a door switch. so how to i trace this down myself before giving up and taking to a dealership?
any advice greatly appreciated.

 

Welcome to the site, it's usually the drivers door switch stuck or broken , this is a general repair how to

 

I don't know what a LCM is. If it's a Light Control Module there isn't one.

What about the dome light?

With or without OnStar?

I guess it could be possible that the RAP relay is stuck, but I can't see how.

Check the other door switches and the tailgate latch. I think the tailgate switch is on the latch inside the door.

 

With OnStar ..
No light control module? assume that leads back to the door switch being the 1st thing to check.

 

All of the doors switch to ground and the BCM does that dimming by controlling the short to ground on a different circuit, so there are 2 routes to ground. The RAP relay controls the hot side.

The wiring diagram doesn't show the on mirror switch.

So, it almost has to be a door switch.

Is the dome light working, not the reading lights the center bulb? It should be on if the courtesy lights are on, unless it is switched off.

 

yes the dome light works.

 

Here is the wiring diagram:

 

thanks for the help :)