I recently removed an non-functioning after-market CD changer from my 99 Grand Caravan. In the process of removing it I shorted something. I can still drive the car without a problem, but some electrical items do not work (radio, keyless remote, interior lights when doors open, etc.). When I just took it for inspection, they were not able to get an exhaust reading when they hooked it up to the car computer. What did I damage and how do I repair it?