* Key Fob Battery: The most common problem is a dead battery in the key fob. Replace the battery.
* Key Fob Programming: If the key fob isn't working at all, it might need to be reprogrammed to the car's receiver. A locksmith or dealership can do this.
* Receiver Issues: The car itself might have a problem with the receiver that picks up the signal from the key fob. This requires professional diagnosis.
There's no hidden code to find; the "code" is essentially the unique radio frequency signal programmed into the key fob and the car's system. If you're experiencing problems, focus on replacing the battery and/or seeking professional help to reprogram or diagnose the system.