This started a couple of weeks ago. I scanned thru forums and googled this and it seems like this happens with GM cars 10 years and older. I replaced the battery and the problem went away for about a week. I was leaving the grocery store today when the security light stayed on. I waited about 10 min till the light went off. turned the key and it engaged. Will changing out the lock cylinder do the trick?

Things I've already done:

1. Battery cables ok
2. New Battery
3. Alternator checked out ok at Autozone

 

what year, engine, etc

 

1998 Lumina 3.1L

 

I think the keys on these have those chips in them, and it could be that the key/chip is worn to the point where the switch can't read it correctly 100% or the time? - Maybe I'm 100% wrong here - but I thought the later 90's GM cars had those "chip keys"

or, yeah, the lock cyl may have a sensor that is dirty/worn and can't see the chip on the key correctly, etc...

I'd start there - maybe the dealer can test the key for you to rule out one or the other? - not sure - I do know the replacement keys are not cheap.