I have been having all kinds of issues with my 2000 Monte Carlo lately. But it is parked outside now since I moved and temps were above 100+ so not surprised. Now trying to figure what all got damaged.

Replaced the Ignition Switch. No if, and, or buts of it being bad. Replaced dual fan assembly. Drivers side motor quit. Tried direct power and no go. But passengers would. Replaced it. Remote receiver was bad. Al warped and chips inside melted. Replaced it. Still can not use FOB though.

Replaced the headlight switch but not so sure it was bad, I just thought so. Was able to move the wiring connecter on it and lights would get brighter inside so figured, okay, switch is bad. Nope. Replaced switch and still have dimming lights inside. I also have ABS and Trac Off staying on.

Is it normal for the lights to dim inside (dash, headsup display, radio) when the Service Engine Soon light comes on?

 

My first impulse says get it to the parts store, have them do a battery/alternator test.

 

My guage for battery does not change from how it always has been. Can run A\C on MAX for a 1300 mile trip, headlights seem as bright as normal, run the radio. Guess I would not have thought battery\alternator to be an issue. Can not hurt to have them checked though. Really hoping someone has experienced this exact same problem and what it took to fix it.

 

I know the last post of this discussion is almost a year old, but by any chance, did you figure out the solution to this problem?I first noticed there was a problem with a relay or a module when one of my headlamps and brake lights gave out around the same time. At first I thought it was a coincidence and blamed the headlights on possibly a bad HID light, but then I soon noticed that the service engine soon message displayed on the dash and occasionally, all of the interior lights go extremely dim. Sometimes they're normal and other times they are not visible which makes it hard to see all the gauges

 

The ambient sensor light at the front of your dash by the windsheild (little bulb that is a little left of the center of the dash) was my dim lights inside issue. I got it from the dealer for under $15 dollars. You just pop up the panel and change. Pretty cheap and easy fix. The sun can burn the sensor if you park the car in direct sunlight I guess. And I am sure age can as well.

As for some other issues, came around to being the ignition switch. I had bought a new one but it was faulty (got it super cheap online, or so I thought ). Bought another from the local parts store and all has been well since then. Took me awhile to figure that one out, thinking it could not be that, part was new. lol I had Trac Off, ABS and Service Engine with ignition switch being bad. It got to the point of issues starting up the car again so took the plunge and bought another ignition switch. Problem solved!