My theory is that everyone that wants to keep their Jeep a while should lay in an extra PCM. Get it at the JY off ebay, whtever the cheapest hookup you can get. If you can land one for less than $50, I'd go for it. The key is to get one while your Jeep is running good. Swap it in and test it out, then put your old one on the shelf in a waterproof bag with dessicant. Sooner or later, you'll wish you had one to swap out to test your latest problem. 90% chance, your old PCM and new PCM are both good, but at least you had a known good on the shelf to swap out. If you buy a used one (or new, refurb, whatever) and swap it in when you have a problem, you won't really know if both had the same problem or not. Verify your back up unit while you are running good!