I have a 1993 Jeep Cherokee. I recently had to change out the house on the front of the head where the radiator and heater hoses attach. The thermostate is also in there. It had a hole from corrosion. I replaced some of the hoses and clamps. I also replaced the thermostat and gasket. I did not replace the temperature sensor (at least that is what I assume it was) that screws into the side and has an electrical connection. I drove it 2-3 times and things worked great. No leaks no overheating. Drove it tonight and while driving I saw the temperature gauge reading was coming up to just under 200. Then started bouncing up/down (never over 200) and then dropped down and was not reading. Check engine light came on. I have not checked the code yet. I cannot find a place that has a older computer code checker. My first thought is it has to be the temperature sensor I did not replace but I was curious on other thoughts or ways to see what it is. I drove it for another 20 mins after gauge stopped reading and gauge never started working but I never saw signs it was overheating.

 

http://www.xjtalk.com/showthread.php?t=11574

try this out and report back with what codes your throwing.

my guess is that you damaged the CTS. i busted mine on accident when i did my header swap as well as the temp sender for the gauge in the back of the head so its a deffinate possibility