I know it's not a Grand Prix but it's still a 3800. I got a buddy with a 04 impala ss and yesterday he was swapping audio amps on his system and somehow the positive touched the ground. Now the car won't start or do anything, nothing works when he turns the key on. Only light that comes on is the engine light. No security light or anything. We have swapped battery's and checked all fuses. What could it possibly be? Any ideas would be appreciated.