I have a 2003 3.4l Impala that just shut down while driving, almost like an alternator but did not loose power to lights, radio, power windows or locks. I tried to restart it when it happened by putting it in neutral, while coasting, but no crank. I pulled over and disconnected the battery for a couple of mins and tried to restart the car. No crank, it seemed to cut power off to my starter and fuel pump, when I took the key out of the ignition my parking lights stayed on and had to disconnect the battery to turn them off. My mechanic said to replace my ignition switch and key cylinder, with passlock, did that with no change. also checked fuses and relays, they are all receiving juice and none are blown. they tried to get codes but would not hook up, says error. my radio is also reading CAM ERR. Thank you for your help. this is driving me crazy, I have found cars that had similar errors but they had after market alarms, I have a base impala and have not done anything to it. thanks again for any and all help.