So I was handed a 1997 Buick Lesabre never cared for free, put lots of time into it and got it working good. To reset engine code I disconnected negative battery terminal...wish I never did. After 5 minutes I put it back and the annoying stock alarm went off. The light attached to the underside of the hood was flashing and blinking also.

I tried unlocking on the remote keychain, tryed turning the key, tried manually unlocking the door...NOTHING.

Now the next day later the car still wont start, battery and electrical are fine, just when I put it to ON position I hear that same blinking as both turn lights on front are going off, but no alarm now. I ALSO tried the turn key to ON position 10 minutes, then off 5 seconds...Repeat 2 more time relearn procedure. NOTHING.

Please help, I work at Town Fair Tire and none of my coworkers have any idea, also called Mcdermot Chevrolet dealership and all they could say is the same key on position for 10 minute thing I did already. Really would like the car to just start again, I hate theft deterrent systems!!!!

does it have a aftermarket alarm or immobilizer?

That doesn't sound like a stock alarm to me......

I bet if he pulled down the hush panel on the driver'* side, a module and a wiring harness would come down with it.......should be looking underneath the I/P panel for a toggle switch......

I have never had a no start due to a battery disconnect, having an affect on Theft Deterrent or Content Theft Deterrent....

Absolutely no aftermarket alarm or anything of that kind, I was told by the GM service tech its not an alarm, but a "theft deterrent system" Dunno what the difference is, but now there is no beeping horn. Only blinking L and R signal lights and that weird light attached to middle underside of the hood. On system functionality such as windows going up and down work, just not a start. Very frustrating and seemingly unheard of to everyone, also NO "Security" light comes on that I read online may be an issue

Did you physically look for an aftermarket system under the dash?

Only blinking L and R signal lights and that weird light attached to middle underside of the hood.

there is no weird "stock" light like that on this car.....

The fact your SECURITY light is NOT coming on, is why it won't start.....there has to be some aftermarket device installed......on a stock vehicle, disconnecting the battery would not cause this to happen....

This is so unbelievably annoying, I redisconnected battery for 5 min and tried again. I tried EVERYTHING. Asked GM dealers service depts, mechanics, engineering friends. It IS NOT an aftermarket install I can stress that enough. The light under the hood that blinks is just stock hood for lighting when hood is opened. NO security light still comes on. Heres another weird but probably useless piece of info....when I went to open the hood (battery still connected for days at this point after initial event) the annoying alarm tone was going off but very faint, as I figured the juice to the battery is draining now. But before I disconnected terminals again I tried to hit the red panic button on remote key switch just for hell of it, that set off a LOUD alarm tone....as if it were 2 seperate systems. But my stepfathers parents bought this car new at GM dealer and I have all the paperwork and they were only owners before me...nowhere does it say another alarm installed.

To the best of the massive input I've gathered, the theft deterrent system here is screwing with me bad and will not let the car start. I need to find out how to bypass. I even checked removing all the fuses and looked under hush panel for toggle Tech II mentioned with no luck. Ready to have it towed away, but if any of you guys wanna take another crack at it or have a faint idea I'll check back here next couple of days. Thank you again for taking time to answer.

-Erik

You could try getting a vats bypass.
GM VATS Bypass Module For LS1 and LT1 [gmvats] - $19.95 : 3rd Brake Flasher Web Site

Or for one that may be easier to install, since you can optionally buy a quick disconnect for it.
Baker Electronix - GM VATS Bypass

if you take a test light and hook the ground clip to battery positive and probe the start enable at the relay from the pcm. you should get a light when someone is turning the key to run, if not have to backtrack up through the pnp and pcm see if you have it anywhere and please report back.

But JW, he says his SECURITY light is not coming on when he turns the key to on......if it isn't, then that decoder is not going to ground that relay.....

Methinks we need a Tech II scan tool to check for ALL possible codes, not just PCM codes...

Have we established if this is PK II or III....does ignition key have a black resistor on it(II)?

Is this LeSabre a custom or limited? Didn't the limited'* come with CTD?

But like I said, I have never seen these systems activated by disconnecting a battery.....only on aftermarkets......

The key fob...is it a GM one or aftermarket one?

most dont have access to a tech2 or want to pay the dealer to diagnose the issue. so if the bulb is burned out and the module is sending the start signal it could just be a bad part in the start circuit. or it could be a bad module, but the checks i posted are a good halfway starting point.