After trying to get security system to work properly, I just ended up tearing out the horn/siren from under the hood. The red light flashes consently on the console, but no siren going off all the time. Problem solved.
Door locks still work, but not with remote - but the remote never worked anyway... yes it was coded to the computer, just never worked. I hate giving up on a problem, but this security/door lock sytem is just a mess on these models and tearing out the siren was in the end the resolution of last resort.