2002 cadillac eldorado horn blows and lights flash everytime either doors are oppened. Security light on dash is not on. Need to stop this from happening any suggestions?

Sounds like the button under the steering wheel airbag or the clock spring iteslf is stuck.

horn button sticking or you have bad horn relay.horn button wire touching ground.

Yes, you need to find the positive wire to the side light circuit, from the alarm and try splicing into it, and then to the horn circuit.
You need to be sure that this wire doesn't also become positive when the side lights are switched manually though.

The security light is supposed to flash, it indicates the system is armed, the system is functional in my opinion, why do you think it isn't? It is not the cause of the drain unless the car sits for months. Check for vanity lites in the visor left on or other interior lights.

Under the carpet, near the gas pedal, there is a ground wire screwed in, and that connection is going to be corroded. Clean up the connection and be sure it is tight. I just went through this with my 97 Seville. Fixed every electrical problem I was having with lights flashing, gauges going crazy, etc...

Either via an actual theft attempt or you (or someone with your keys) not realizing that you/they actually armed the vehicle and opened the door or trunk afterwards.

Essentially this sounds like the vehicle was entered after being armed and the proper precedures not met to reset it.

The car may just need to be locked from the outside with the key (not the remote or keyless entry) while the doors are closed and windows are up, and then also unlocked with the key...

However it sounds as though you have perhaps driven it since then. If this is the case

You may want to check all your fuses and replace the ones affected by the anti theft system.
Security - Pwr Locks - Horn - Pwr Trunk Release _ Int Lights - and maybe The Emergency Flasher as well.

Be sure and check under the Dash, Hood and under the Back seat.

Cadillac recommends after a theft attempt, the vehicle may need to be serviced. So I recommend going through the fuses first, even replacing the battery in your remote fob and then if the problems still persist. have the vehicle serviced.

Good Luck and Happy Motoring

Respectfully

The SECURITY light is located on the instrument panel cluster.

If the ignition is off and any door is open, the SECURITY light will flash, reminding you to arm the system. To arm the system, do the following:
1. Open the door.
2. Lock the door using the power door lock switch with the door open or the remote keyless entry transmitter. The SECURITY light should come on and stay on.
3. Close all the doors. The SECURITY light should go off within approximately 30 seconds. If a door or a trunk is opened without a key or a remote keyless entry transmitter, the horn will sound and the lamps will flash for about 30 seconds.

Also can check this and other details in the 2002 Cadillac Owners Manual (page 85 and next).

Hope helps (remember rated and comment this).

try using the key on the passenger side.

take the cable off the battery to reset everything,it should work.

you cant just diconnect it....you may try locking and unlocking the door with the key ....that may disable the alarm otherwise you may need to get it to the dealer for further diagnostics