Do you by any chance know what the DTC that your Mechanic got from your Jeep?. If it is a P0356, then you would need a PCM. Pros and cons with a Used PCM. It's Cheaper from a junkyard, however, it has to be re- programmed by a Dealer. depending on the used PCM vs. your Jeep Configuration will be contingent on how much they will need to do to re -configure that pcm on your jeep. That would mean, the dealer might charge you by the hour , however long it would take to make it work. A new PCM will only require the VIN to be programmed and the Security PIN IF it's a Skim equipped Veh. I hope this Info helps you make your descision.