I have a 2001 throwing code P0340. The battery light was on so I replaced the alternator with a new one form American Muscle (the $100 one). The battery light is now off, but I am still getting the P0340 about every 2 weeks. I just had the alternator tested at Autozone and they said the alternator was fine, but the battery was low. The car is displaying symptoms of a bad cam shaft position sensor with a stumbling idle, runs very rough below 2k rpm (sometimes, especially when it rains), and every so often it is hard to start unless i press the gas pedal while starting. Could this be a true sensor problem? Or could this be from a bad battery? Are the $100 alternators from American Muscle junk? Any help would be appreciated.