I've read that it's likely the circuit board has developed cracks on the solder joints. You can try to visually examine it and clean it first. If that doesn't work, you can try to resolder all the joints (surface mount).

 

What do you mean your key battery only lasts a week?

FYI, if you don't use your car for a week, the key fob will not work, it is shut down to conserve battery power. You have to use the key in the door, then the fob will work again until it sits undisturbed for a week, then the fob will not work.