It's the crank sensor!
Join Date: Nov 2007
Location: Central Minnesota
First question that needs to be asked that could be related is this. Are you having to add any antifreeze to your coolant reservoir? Unexplained coolant loss on the 00-01 can be caused by a cracked 0331 cylinder head. Not saying that is your problem but I am saying that you need to watch your coolant use like a hawk. Are you aware of the 0331 head issue on the 00-01? If not, GOOGLE is your friend and you need to educate yourself about it.
First off, any low oil pressure readings on your dash gauge should be verified. Never guess or trust what you are seeing on your dash. Go to your local parts store and rent a "mechanical oil pressure gauge". They can be rented pretty inexpensively.
Remove your oil pressure sending unit (located right above your oil filter) and temporarily install the gauge there. See what the mechanical gauge reads. If your oil pressure truly is low, then you will want to perform some more testing to decide the proper course of action. However, if pressure is within spec, then replace the oil pressure sending unit as they are a very common failure on the 4.0
The oil pressure spec. for the 4.0 is as follows:
*Not less than 13 psi at HOT idle
*Between 37-75 psi OVER 1600 rpms
TEST your way to determine root cause here. Good luck and keep us updated!
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!