Keyless entry alarm

Are the keyless entry/alarm systems compatible with a 90 Cherokee laredo?

You need to find out if your Jeep came with that as an option. On my 97 there is the sensor right behind the rear view mirror. It is a plastic bludge type thing sticking out of the headliner. Try to get your hands on your build sheet to see if it had that as an option. If it did then you need to find the proper remote for that year. I'm not sure what they look like, I've never seen one for a 90/ Ebay is a great place for that. Or you can have an aftermarket one installed, but take it to a good shop because a bad shop can really fawk up your wiring.