I saw your post in the WJ section about the problems you're having with your car. I'm not sure about the ZJ's, but a problem like this would have me replacing the CKPS. This is a common failure on the WJ 4.0L's. Just because you're getting spark doesn't mean the CKPS is good. If you're getting gas and proper spark I would look into the smaller items before your PCM. I would unplug the connections and make sure they're clean, but after that I'd look somewhere else. This is, of course, not to say that this isn't your problem. It could even be your battery (I would return the one you bought and buy the proper one). Other than that, I'd look more about the fuel, use a noid light (plugs into the injector harness and blinks when the injector is grounded by the PCM). Other than that you're gonna have to take it to someone who can hook your car up to a scan tool and check more in depth.
I almost forgot, any hard codes?