Originally Posted by Keith333

I've been experiencing the same intermittent problem (comes and goes) with my 2000 4.0L the past few weeks, and it did it again this afternoon when I got home. The engine has always sounded perfectly fine when the gauge reading has dropped and I've always suspected this was either a wiring or sending unit problem, and not mechanical, so when I got home this afternoon I left it running (with a near zero reading) and simply separated the wiring as best I could immediately out of the unit connector and the pressure rose back up to the usual 40 reading. Now if I can just figure out how to get the harness disconnected from the sending unit, I can get better access to the wiring harness and clean things up and insulate the wires.

I'd suggest you try this as well and hope it solves your problem as well.

Related question to all: How in the world do you disconnect the harness from the sending unit? It seems like it should be much simpler than it is... and probably is very simple once you've done it.

Originally Posted by Roler

And how about actually verifying that low pressure, with a pressure gauge !?

Originally Posted by Glockmeister

There should be a red tab on the connector. Just push it and it will click to the other side and unplug the connector.

Originally Posted by salad

Comes up about once every two days here. You can add "site:cherokeeforum.com" to anything you type into Google and get results only from here. Also we'll forgive that you put this in Cherokee Chat and not OEM Tech

But, since you can type properly and seem nice, here are some key questions and suggestions:

- When was your last oil change? What did you use? Improper weight can cause issues.
- What filter is on there? FRAM, STP, Quaker State, basically anything really CHEAP will cause problems like this including damage to your engine. Mopar, Purolator, WIX, NAPA Gold, Carquest Blue, and anything that's better priced are safe bets.
- Does your oil pressure gauge move when your engine isn't running? It should be zero with the key turned to ON.

- The little passageway inside the engine block that feeds the oil pressure sending unit can clog with sludge that will screw with accuracy. Unscrew the oil pressure sending unit (located just beside the oil filter) and jam a pipe cleaner down the hole. Make sure it's clear.
- The connector can also get plugged with crud or wiring abraded causing a false reading. Remove the connector on the OPSU and spray it out with brake cleaner, make sure it's clean.
- Oil Pressure Sending Unit is notorious for going out and causing this false reading. If all else fails change this.