OK, here I am again. With the help of this forum, I'm learning how to fix this new Jeep. (To me an electronically controlled 1999 is a new car). Yesterday I took her for a short drive and the 'check engine' light came on. First time it came on, so I might finally pull a code or two. Heading back home the 'check gauges' light came on. All the gauges were fine EXCEPT the most important one. Oil pressure read zero. Then it came back up and the 'check gauges' light went out. Back and forth back and forth like this all the way home. Today she started, showed no 'check engine' light, no 'check gauges' light, everything perfectly normal. All grounds have been cleaned. Your expert thoughts on this are welcome.

 

It might be as simple as a bad oil pressure sending unit.

 

Plug in the scanner and pull the codes. You should be able to see recent codes even if the CEL is out. It also can throw codes and not trigger the light as well.

 

Had the same problem on my (former) 98. It was a bad sensor. Hope for your sake that's all it is. Good luck

 

Welcome to the wonky '97-'01 electrical issues! Where you get to confirm your finicky guages all the time.

At a minimum, check those codes just in case and clean up your three ground connections. If your oil pressure sending unit is being weird, it would be a good idea to rent a mechanical pressure guage and confirm that everything is ok.

Same thing happens in my dad's 98. Just this morning the oil pressure was bouncing back and forth on my ride to work, then it sits at 10psi for the end of the ride. I pulled into the lot, rev'd the engine and it never moved. I opened the hood, wiggled the oil pressure sending unit connection, got back in the cab and rev'd it. It raised to the normal level. So even though your oil pressure sending unit might be good, your connection could be bad.

It's also possible your guage cluster connection in the back is corroded. There are easy ways to clean it up but not as easy as the other stuff that's listed in the thread. Start with the easiest first. My 98's cluster drops all the time. I honk the horn and it comes back up.

 

Thanks to all for the replies. Certain the problem is electronic and not mechanical because I did screw in a manual gauge to be sure. I pulled the sending unit and cleaned everything just to see if that might solve the problem. It did not so time to pull some codes.