dead battery. HELP? I had the crankshaft sensor in my nissan sentra replaced. I get a call from the shop saying that my car is ready but I have a dead battery and it won't hold a charge. I go and jump it and I get it started bring it home. Shut the car off and try to start it again no power. I've replace the battery and it still does have enough juice to get the car to crank over. Could it be the crankshaft sensor causing the problem? HELP