New to the forum and the world of Jeeps. I recently purchased a 2000 XJ, 4.0, Auto Trans that was missing the ECU/PCM. I purchased a used ECU (P56041 638AD) online and plugged it in. Where the original one is missing I am not sure how to figure out which one I should have in there and this may be the cause for all of this. If anyone knows a way that I can figure that out please do. When I turn the key the fuel pump primes, the starter will crank, but engine does not turn over. I pulled the coil rail off and checked for spark by putting a spark plug in and grounding the spark plug. I have no spark. IT seems the CPS is a common point of failure so I checked pins "B" and "C" i get minimal resistance (4.5 I think) so I think it is good. The cluster back lights work but none of the gauges move. I have pushed and held the trip reset while turning key to on and the gauges all do there happy dance. I am also getting the dreaded "No Bus" error on the odometer after 30 seconds. The Engine only has 132,000 so I think this old girl should have plenty of life left in her.....