3. Our ECM was scanned to make sure it didn't have a security system that would lock it up. We also received the VIN and the factory build sheet for the Grand Cherokee that once sat behind this computer (this is important info to have if your engine swap needs to pass a DMV referee). For safety we mounted our ECM on rubber bumpers (rubber stoppers from the local hardware store) to take some of the shock out of harsh driving. Hotwire also provides new computers and can program used ECMs.