Which type of harness do you have? If it's the older type (the one that is hard-wired) then check and make sure that it is connected snugly. If some how it wasn't connected (where you here it click) it could've backed itself off. If that's the case then it will not run.
Otherwise, if it's connected properly then it would be the Unichip. Just make sure that you look at the wires and that none of them have broke loose.