I should have asked, I'm assuming a 4.0. The reference below is for a 4.0, the 2.5 it the page before but the wiring is the same.
Do you still have the part that attaches to the sender? It looks like the ’99 has 3 wires. 2 go directly to the PCM & one splices with other wires before going to the PCM.
Go here to an online read only FSM. Pick your yr & the sensor is shown in the fuel/ignition system (section 30 about page 8). It is called “engine oil pressure sensor” if you look it up in other sections. Go to the connector pin outs section to see the pin locations. The 3 PCM modules are shown there (section 80 about page 30).
Jeep Knowledge Base