I have a 98 deville i installed an aftermarket head unit and speakers. Well everthing seems to work fine but last night i went to my car to get something and the doors wouldnt unlock i opened it with the key and found out the car didnt have any power. I tried to start it and everything came back on but all the info was set back to 0 like used gallons, trip miles, miles to empty etc. It was like when you unplug the positive in the battery and everything erases. Anybody knows what could be causing this thanks in advance.