I got this 2004 Monte last year. A couple of times the security light went on while driving. Did not affect vehicle operation. On next vehicle startup the security light was off.

Last month i took the car in for state inspection, oil change, filter replacement.nothing to do with any electronics. After the technician finished with the car he parked it and shut it off [was running for like 30-45 minutes on the lift and when he did the emissions inspection. Ok so i paid for the repairs. Go to my car turn the key , car DEAD as a door nail. Had lights but no ignition, no crank, no nothin. The Security message appeared on the instrument cluster. After several attempts by the tech, his boss came out, and he turned the car off and then tried to start it, and it started! No security light. Weird. He said that it might be the key cause the key i got with the car is an Axxess brand key ,not a factory key. Doesnt make sense to me since the car ran fine for a year with that key.

Anyway, car starts and runs fine. Today i noticed again the security light comes on while im driving on the highway. Vehicle operation seems normal. Even tried to restart it and the car started again, just that this time, the security light came back on after the battery light went off. I'm hoping that the car will start in the morning.

Does it sound like this car is having the burn wire contact issue, that has been mentioned on this thread? Oh also, i don't know if this is related but 3 times previously while decelerating from highway speed while exiting the highway, the bell chime would sound numerous times, until the car came to almost a stop. Never experienced this with any other cars.

Any advice would be appreciated as i am trying to avoid a future disaster requiring the car to be towed off the road while i am in it. Thanks.

Next morning, started the car normally, no security light, Drove it all day.

Watched a video on Youtube about this and he called it "Fuel Enable Mode" since the car was started with a successful key cycle but something happened while driving that changed that voltage which runs through the yellow wire , turning on the security light. Just a novice at this trying to learn how the passlock system functions.

2004 Chev Monte Carlo SS, 3.8 litre engine, 54,000 miles

 

Look up GM Pass Lock system. There are several videos, articles and blogs on the subject. It could be that you have a bad connection at the Pass Lock/ Body Control module.
My Security light comes on when I hit a bump. Then goes of after the car has been sitting for a while. As an electronics tech, this sings to me as a bad connection. I also have to do a Security Relearn every now and again! The key doesn't matter. The resister for the security system is in the ignition not the key.
Some of the videos and even a couple of threads here will explain how to do a Security Relearn and how to replace your BCM. And there are some articles explaining the loss connection! Good luck!