Hi guys. I have a 1998 DeVille. Beautiful car, great condition and about 150,000 miles. Some time about a year and a half ago the car had a dead battery when I went out to start it in the morning. I charged the battery and the car started then shut off giving me the message on the HUD "theft system problem, car may not restart" (something like that) the car will start again if you wait 2 or 3 minutes but then do the same message. There is watter getting in the car but I'm not sure where or how. I pulled the carpet back a little in the front and found the firewall feels wet. If I just keep the battery charged and check it from time to time, out of no where it will all work again. When everything is working the battery is fine but when the car is having this problem the battery will not stay charged. Something is draining it. I did put in a new battery just for fun. When it has this problem there is a lot that will not work. Key fob, button to open gas, button to open trunk, stereo say "lock", heater controls and HUD are blank and computer is set to metric. I keep it on the charger when it is doing this and just hit the lock button on the key fob from time to time as I walk by and one day out of the blue the horn will give lock tone "single honk" so I use the fob to unlock it, get it and start it. All is working and everything is great. When it is not working and charging, it could be the next day or 4 months before it works again.

Things I should make note of

1. I live in Washington State. Lots of rain.
2. Every time the car have this problem the battery is dead.
3. Could be 4 hours or 4 months before the car works again.
4. The blower motor quit working about 2 years back.

I don't know what els to say. I know the post is long. Thank you for taking the time to read it.

there is a how to on chasing a drain, cant find it for some reason. but you have to take the pos cable loose and set your meter to current or amps when you are having the issues and start pulling fuses and relays until you have a significant drop in current reading. the bcm sounds like its your symptom causer but may only be messed up because of the low power situation that may be caused by something else. then again maybe something in the bcm is bad causing a large current draw, you will have to do the test and go from there.

thanks for the reply.

I did however replace the BCM the 2nd or 3rd time the car did this.
Everyone said it was the BCM and after lots of money it was not

I think you are right that the BCM is doing something but like you said,
it may be doing it because of a draw or open relay. I have thought maybe
the anti theft system was turning everything off and locking the radio but
thats back to "what is the root of the problem"?

Like I said, I think the water is the prob but what is the water getting wet
that is causing the draw or theft system or..... whatever it is doing......

https://www.gmforum.com/showthread.p...light=amp+draw

i remembered where the post was, yep if you already know its not the bcm itself you wont know till you do the test

I did the test and found about 0.43 to 0.28 draw.
From time to time it will go up to 1.56 for a short time then drop to 0.43 - 0.23
The relay marked "intermittent" is staying charged all the time.
I don't know if it should or not. When I plug in the battery it clicks.

that dont sound too bad. was it malfunctioning at the time you took those readings? i dont know what intermittent is and i dont have any diagrams for that car unfortunately

it is not malfunctioning at the moment.
The trunk would not pull down last night but it did close.
This morning when I went out to look at it the trunk was pulled down.
Some time in the middle of the night it decided to pull down.
I don't know if this is all the same problem or not but it has never done this before.

sometimes the contacts get dirty. those things aggravate me, and it doesnt seem like there is any point. the one on my firebird doesnt latch unless that thing is working.

I have found all the probs and fixed them.

There was a factory cold weld in front of the windshield where the fender and firewall meet. The cold weld cracked letting water in the car. The water would flow under the carpet and soak in like a sponge. The air bag computer sits under the driver seat. This is what was getting wet causing the battery drain and the theft system to kick on.

Thought I would post the fix being I hate it when you follow the forum and never get the answer....

thanks for updating