Oil pressure isn't the only indicator of head gasket failure, the most common indicator of failure in the 4l is coolant in oil. You can do a cylinder leak down test which not only indicates bad head gasket but can also tell you if you have bad valve seats, worn piston rings and will tell you if you're losing compression..
It's also worth noting that 00-03ish cylinder heads are prone to cracking due to excessive heat build up. Most commonly they will crack between cylinder 3 and 4. If you're due for an oil change soon do it yourself and check for milky/mocha color in your oil, which usually isn't seen until it's almost done draining. Often times it's not even seen on the dip stick either.
If you don't find any I would still do a leak down test (or take the Jeep in to have it done) just to rule out any possible problems