How to Fix a Key Fob That isn't Working
If your key fob won't work and you're not sure why, you can fix it with a few simple steps. The first step is to be sure that it's not your 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 circuitry or battery issues.
Battery
The battery inside the key fob may wear out over time. It is easy to replace batteries. However, it is important that you use the correct kind. You can consult your owner's guide or contact the manufacturer to find out the right kind. It is also a good idea to inspect the battery compartment carefully since dead batteries may leak caustic chemicals that can cause damage to the remote. If replacing the battery does not fix the problem there could be other issues requiring professional attention. For instance, if the buttons appear stuck or damaged it could be necessary to disassemble the remote and rebuild its components. You could also try reprogramming your car to recognize the new key fob.
Buttons
Through repeated use, key fobs can become worn and dirty. It is not unusual for buttons to cease functioning, or require a hard press to get them working. This can be very frustrating, especially when you are away from your home and have to turn on your car. Even broken or damaged buttons can be fixed with a little effort and materials you already have at home.
First, verify that the batteries have been correctly installed and that the indentation on the back of the button is filled. Then, open the remote with care and inspect the circuit board. Look for indications of rust or other signs the buttons are damaged or worn. For instance, conductive paint may be missing. Use a Q-tip dipped into rubbing alcohol to gently clean any membrane contact that has become damaged or where conductive paint is missing. Don't rub too hard as this can damage the conductive paint, and block the button from firing when you press it.
Also, carefully check the battery connector terminals for an unattached solder connection. Soldering them back into place will allow the button to function again If this is the case. You can use the same process to restore functionality to any other loose connection inside the fob.
Finally, if any of the buttons made of rubber on the front of the key fob have stopped functioning or require a difficult press to function it is likely the graphite disks at the back of the button are deteriorating and need to be replaced. This is usually done by rubbing a pencil over the disks, which will bring the button back to its original state.

If none of this is useful or if the button still doesn't respond to a firm press It could be that the circuit board is damaged. This can be fixed with a quick clean and replacing the solder, but it is best to have an extra fob available in the event this method does not work for you.
Circuitry
If the key fob buttons function, the circuit board inside your remote might be dirty. A thorough examination is often enough to resolve this problem. The most common causes of dirty circuit boards is water and damaged cases. A broken case can let water and other debris to get into the circuit board, causing it to short. Water can also destroy pins and connectors that are small on the board, referred to as via's.
If you're able to open your key fob, and you're not afraid of making a mess, we can remove the solder from the buttons and then solder new ones in their place. Also, it's worth checking the connections between battery terminals. If they are loose, the buttons might not work or even become stuck in their down position. Soldering the terminals and buttons back in place is usually all that's needed to return a non-working key fob to working order.
Non-Remote Transponder Chips
The non-remote chips sealed in a sealed case are more durable than remote fobs. However, they can be cracked in the event of a hole being drilled in them or in the event that a door handle of a car or lawnmowers is pushed over them. Fuse failures are usually to blame for non-remote chip failures.
If you're not comfortable opening the key fob, take the circuit board off and use a multimeter to verify that the diode is working correctly. If you don't feel comfortable with this, visit your local Oreilly or hardware store and test their RF frequency tester. car keys repair will inform you whether the key fob is sending a signal.
Programming
Key fobs aren't indestructible and are susceptible to being damaged by a variety of factors. They can lose their pairing to the receiver in your car because of shock or a low battery, which calls for them to be reprogrammed. A professional auto locksmith, or main dealer, can reprogram your keyfob and get it up and running again. If resetting or replacing the keyfob is not working it is possible to replace it.