Hi I have a 2002 monte that acts possesed..lol,the headlights and reverse lights will flash on and off all day and night..Dont have a clue of why this would be happening..Hopefully someone can help me with this,,very aggravating and killing my battery

 

My first bet would be the BCM or something in the security system. Any other issues? Look up a security re-learn procedure for the pass lock system. But also try leaving the battery unplugged for 30 mins or so. Iv never heard of this problem but know how some systems work thoes are good things to check. Do you have a security light or any other warning lights on the dash?

 

No security light on only other light that comes on is my battery light...dont know why,altenator works fine,enen did most common test and took positive cable off while running and had no issue.

 

Have you had the battery and alt tested? Could be a poor grounding issue as well.

 

Brand new battery..and had alt checked 3 times just to make sure

 

I had an issue with my '04 that if I did not drive it for a couple of days the battery would go dead. When I switched the backup lights in the bumper cover with LED lights, I noticed when the battery would go dead, they would blink (never noticed the headlights blinking). Since most of those items go through the BCM, if the car doesn't have enough power, computer gear can do wacky things.

This nonsense went on from '08-'13 (since I only drive it in the summer, limited time to investigate and it's not like I didn't drive it frequently).

End result, bad battery (fall of 2012), then a bad alt (early summer 2013) and a bad battery (under warranty later on in 2013). I believe for me, it's case closed, as it had a couple of times where she sat for a week straight and no dead battery.

I would advise against doing that test. On older, none or lesser computer controlled cars it was not a big deal. But with more modern computer controlled vehicles, this runs a risk of damaging sensitive electronics.

Also it does not prove if the alt has a "leaking" diode.

Have the battery and alt bench tested (removed from the car). But keep in mind, the bench tests are not always 100% on them. For example (spare the long story), my alt failed a bench test at one store, passed a bench test at two other stores and then PASSED at the store that failed it. I finally replaced it when it began "stinking" (smelled like burning electronics from time to time).

 

Did bench test on both tonight at local autozone..passed so i asked them to test 2 more times..passed them also..so im starting to think it is the bcm

 

And if its a ground issue ive been through it over and over

 

BUT before you go replacing a bcm (expensive and alot of work) It could also be the headlight multifunction switch... if something is shorting in the SPTT switch could be why they are turning on and off. Sorry that just came to me.

Another thought comes to mind that when i was connecting my battery the other day it caused my headlights to flash on when i first connected it....

But start with the switch pull it out and you should be able to get an idea of whats supposed to have continuity and whats not. Do you have a multimeter? You can buy one at radio shack or just buy a new switch (honestly both probably about $20 each, if you buy the switch used)

Here is a link Monte Carlo Headlight Switch Control Impala 00 01 02 03 04 05 Chevrolet 483 | eBay

 

I looked at the headlight switch and it seems to turn on fine,but when i go to dim the dash lights,they dont dim they just go out completely