Security ssystem

I just picked up a NEW to me XJ from my dad in Hackettstown NJ today.
He gave it to me because he can't keep it running. The security system I believe is the cause. In the passenger door is a yellow piece with wires that connects to the door lock. When I unlock the Jeep the lights flash and the horn sounds as if it has been broken into. When I turn the yellow piece to off or lock and back it disarms it. It will occur at anytime. If it starts it will stay running but if you shut it off it may not restart.
My bro-in-law installed a stereo several years ago and the problem started then. He(my dad) has been trying to fix it since. He is fed up and told me to come get it that it is now mine.
So, any thoughts as to what may be causing this?
Is there any way to completely bypass or eliminate the security all together?
Oh, the yellow piece with wires has been replaced already.
Thanx for the help.
Stukboy

What year XJ? There are some options here, is it after market, dealer install or factory install?

One of my daughters lives right up the road from you, in Highspire.

OOPS!! Guess that info might help. It's a 92 limited. Factory installed with that infrared dot on the headliner.

You will need a genuine Jeep Factory Service Manual for your Cherokee to diagnose or repair.

You may be able to eliminate the anti-theft system by removing the anti-theft module and installing a used non-anti-theft enabled PCM.

Read this: http://answers.yahoo.com/question/index?qid=20100206115922AA91mCM

When you say unlock the Jeep and the alarm goes off are you using the keyless entry or the door lock? I don't have a wiring diagram for the 92 but do have one for a 93.

The keyless entry module, the drivers side door key tumbler, the passengers side key tumbler and the hatch key tumbler all go to a switch then to ground (the key tumblers have a switch built in) when used and disarm the security module. Likely the same with the little yellow disarm switch you mentioned. In effect a ground pulse disarms the system.

Best guess is one of the switches is faulty, rusty, corroded or whatever and making an intermittent ground path. Next best guess is you have a ground fault, look up Cruisers ground refreshing and check out the ground behind the drivers side kick panel. In many models it is up high above the hood release.

The failure to start or restart sounds like a CPS problem. You may have two unrelated issues here.

Though it may be something in the security module or even like mentioned before a flaky switch randomly pulsing (or failing to pulse) the security module. I had an issue with my security module (in my 96) poor contact at the connector. I don't know the location for the security module for your 92, I'd find it and unplug the connectors, check the pins are all the way in and re connect, making sure the connector plug is all the way in (happened to me).

Check the simple and free stuff first, then move on to the exoitc and costly stuff.

The security module for my 96 was discontinued and unavailable. Seems the only source went out of business. But mine was a dealer install and not a factory install.

I'm guessing your 92 is basically the same as a 93, I may be wrong.

www.autobooksbishko.com for legal reprints and CDs with factory service manuals.