so while crawling around under the xj changing my rear main, i couldnt help bu notice that there is a plug that has been disconnected from right above he oil pan. im assuming that this is for a sensor of some kind, but even though its not connected, im not geting any lights in my cluster. im curious whether or not that this can be detromental to my jeeps health

 

Get a pic

 

Photo will help, but it sounds like it might be the oil pressure sender.

 

Oil pressure sending unit is above the oil filter, not near the oil pan.

 

What side of the engine is it on? My guess would be knock sensor.

 

its on the driver side. Its right above where the oil pan mounts to the block

 

knock sensor.. Renix has them, later years dont.
They go bad after a while and people just unplug them.

 

would there be any good reason for me to replace the sensor and wire it?

 

If you want to. The renix ecu is actually pretty smart. The knock sensor was used so the ECU could advance timing until ping starts, and then back it off just enough to where it would run without detonation. Along with properly working oxygen sensors, this brings you some pretty good gas mileage.