I'm working on my son's 2001 Cherokee Sport. A couple of days ago I accidentally created a short from the battery to the cylinder head. I will never work under the hood again without disconnecting the battery!

Anyway, after that I could not get it to turn over. Did a little troubleshooting and found the PCM was fried. I replaced the PCM with a used one. Now when you turn the key to run the starter cranks and the engine fires up fine.

I pulled the starter relay and turned the key to run & start and nothing. I believe this is telling me that the starter relay is energized when the key is in run position and it should not be.

I am assuming this means there is a short somewhere in the circuit. Can anyone help me with finding the short or correct me if my assumption is wrong?

 

On older units the start relay was controlled directly by the ignition switch, later XJ's like yours are probably the same. I'd bet the problem is in the switch.
Try swapping start relays first just in case the problem is in the relay itself.

 

The starter relay is only energized in the start position of the switch.