How to Fix a Key Fob That isn't Working
If your key fob doesn't work There are a few simple steps that can fix it. The first step is to make sure it's not the backup remote.
If the backup can lock and unlock your car doors, then there is likely an issue with the primary remote. The most frequent causes of key problems with your car remote are issues with the circuitry or battery.
Battery
The battery inside the key fob could be worn out over time. It is quite simple to change out the battery, however it is essential to ensure that you select the correct one and you can consult the owner's manual or talk to the dealer of the manufacturer to find out what kind of battery you need. It is also important to check the battery compartment, since dead batteries can leak caustic chemicals that can harm the remote. If changing the battery doesn't fix the issue there could be other issues requiring professional attention. For instance, if buttons seem to be stuck or damaged, it may be necessary to disassemble the remote and rework its components. You could also try reprogramming the vehicle to recognize the new fob.
Buttons
Through frequent use, key fobs may get dirty and worn. This is not unusual however it can cause buttons to cease working or require a very hard press for them to function. This can be very frustrating especially if you're away from home and need to start your vehicle. Fortunately, even worn out or malfunctioning buttons can often be fixed with just a bit of time and some of the materials you might already have in the home.
First, make sure the batteries are charged correctly and that the indentation on the back of the button is filled. Then, carefully open the remote and look at the circuit board. Examine for indications of rust or other signs the buttons are damaged or worn. For example the paint that conducts electricity could be missing. Then, using a Q-tip dipped in rubbing alcohol, gently clean any membrane contacts that have become damaged or where conductive paint is missing. Do not rub too vigorously in order to damage the conductive paint and prevent the button from firing when you press it.
Also, make sure to inspect the battery connector terminals for a loose solder connection. If this is the case, connecting them back could restore functionality to the button. The same procedure can be used to restore functionality to any other loose connections in the fob.
In the end, if any of the buttons made of rubber that are on the front of the key fob aren't working or require a long press to function it is likely the graphite disks that are on the back of the button are wearing down and require replacement. You can usually do this by rubbing a pen over the disks. This will bring the button back to life.
If none of this is useful or if the button still doesn't respond to a firm press, then it may be the case that the circuit board itself has become damaged. This can be fixed with a quick clean and replacing the solder, but it is ideal to have a spare fob available in the event this method doesn't work for you.
Circuitry
If the keys fob buttons are functioning, the circuit board inside the remote could be dirty. A thorough inspection will usually resolve this issue. Broken cases and water are the most common causes of boards that are dirty. A broken case can let water and other debris into the circuit board, causing it to short. Water can also destroy pins and connectors on the board, which are known as via's.
If car key fob repair enough to open your key fob, and you don't mind making some mess, we can remove the buttons from their sockets and put in new ones. It's also worth looking at the battery terminal connections. If they are loose, the buttons might not work or even become stuck in their down position. Soldering the terminals back into place is usually enough to return a malfunctioning fob back to working.
Non-Remote Transponder Chips
The non-remote chips sealed in a sealed case are more durable than their remote fobs, but they are susceptible to cracking if a hole is drilled in them, or in the event that a door handle of a car or lawnmowers is pushed over them. Failures of the fuse are typically to blame for non-remote chips failures.
If you are not comfortable opening the key fob, take the circuit board off and use a multimeter to check that the diode is operating properly. If you're not sure with this, you can go to your local Oreilly or hardware store and test their RF frequency tester. This will inform you whether the key fob is sending a signal.
Programming
Key fobs aren't indestructible and are susceptible to damage by a lot of things. They may lose their connection to the receiver in your car due to shock or low battery, requiring them to be reprogrammed. A professional auto locksmith or main dealer, can reprogram your key fob and get it back up and running again. If resetting or repairing your keyfob does not work it may be necessary to replace it.