My CMU is no longer communicates with any scanner after reversing jumper cables. The radio fuse in back of radio had to be replaced. I have a relatively new central monitoring unit that was installed on a 10 year old A8L and it read out all the codes to any appropriate scanner prior to the short. I checked the fuses in the plenum where the CMU and every other fuse stated in the owners manual and there are no fuses blown, other than the radio. If CMU does not communicate with a scanner are there other diagnostic tools to diagnose the condition of the CMU or does a CMU have only two conditions like a fuse, that is, it either works or does not work? If I need to replace CMU what is the installation procedure?