Ok, so I was having issues with one injector not firing. After doing all tests and tracking down all possible leads it was determined the PCM was bad. Being as money in my world doesn't grow on trees I went shopping for a deal. Did an online search at the local U-Pick-It and found they had a 99 on the yard so I went and got the PCM took it home and installed it. Motor wise everything preformed as it should, all injectors firing again, VICTORY!! Not so quick. Going back inside the cab I now see the oil pressure gauge is not showing anything. No big deal the sending unit is shot, but after 2 different replacements have been tried still showing nothing. Could it be that because my Jeep is a 97 and the donor for the PCM was a 99 that is not able to communicate with oil pressure sending unit? Any thoughts would great. Thanks in advance.