I've replace the batteries in the fobs but the car doesn't respond at all. I can still drive by inserting the fob into the slot and interestingly, the car will respond to the fobs for about 24 hours after the car has been driven. Is the the system battery powered at all by a separate battery to the main one? It sounds like when the car has been used, the battery is topped up but isn't holding charge for very long. Any ideas or is it a new receiver module?