How to Fix a Key Fob That isn't Working
If your key fob isn't functioning, a few easy steps can be taken to fix it. First, check to make sure it's not your backup remote.
If your backup remote can lock and unlock the doors of your vehicle, it is likely that the primary remote isn't functioning. Most problems with car remote keys are caused by battery or circuitry problems.
Battery
It is not unusual for the battery inside the key fob for cars to wear out. It is quite simple to change out the battery, however it is important to ensure that you choose the correct type that you can refer to your owner's manual or contact the dealer for the manufacturer to find out the kind of battery you need. It is also essential to check the battery compartment as dead batteries can leak caustic chemicals that can harm the remote. If changing the batteries does not solve the problem it could be because there are other issues that require attention by a professional. For instance, if the buttons appear stuck or damaged, it may be necessary to disassemble the remote and rework its parts. It is also possible to reprogramme the vehicle to recognize the new device.
Buttons
Key fobs can become filthy and worn out due to frequent use. This is not uncommon, but it can cause buttons to stop working or require a very difficult press to get them to function. This can be very frustrating especially when you're away from your home and have to start your car. Even worn-out or malfunctioning buttons can be fixed with a bit of time and tools you already have at home.
First, make sure that the batteries are properly placed and that the indentation on the back of the button is filled. Open the remote carefully and inspect the circuit board. Check for indications of rust or other signs the buttons are worn or damaged. For instance the paint that conducts electricity could be missing. Then, using a Q-tip that has been dipped in alcohol to 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.
Examine key fob repairs for any loose solder connections. If this is the case, connecting them back may restore function to the button. You can follow the same process to restore functionality to any other loose connection within the fob.
If, for instance, any of the buttons made of rubber on the front of the key fob aren't functioning or require a difficult press to function it is likely the graphite disks at the back of the button are deteriorating and require replacement. This can be done by rubbing a pencil over the disks. This should bring the button back to life.
If none of these solutions work or you are unable to get the button to respond when pressed hard, it is possible that the circuitry is failing. It is possible to fix this by cleaning and re-soldering your fob, but you should have a spare in case it does not work.
Circuitry
The circuit board in your remote control may be dirty regardless of whether the buttons on the key fob function or not. This problem can be resolved by a thorough inspection. Broken and damaged cases are the most common causes of dirty boards. A damaged case can allow water and other debris to get into the circuit board, which can cause it to short out. Water can also eat through pins and vias, which are the tiny connectors that are found on the board.
If you're handy enough to remove your key fob and aren't afraid of a little mess, we can take off the buttons and solder new ones in their place. Also, it's worth checking the connections between battery terminals. If they're loose, the buttons could not work or even become stuck in their down position. Soldering the terminals, and putting the button back in place is usually all that's required to return keys that are not in functioning condition.
Non-Remote Transponder Chips
Sealed non-remote transponder chips are much more durable than the remote fobs that have them but they can be cracked by a hole drilled into them or run over by a lawnmowers blade or door handle for a car. Fuse failures are usually the cause of non-remote chip failures.
If you are not comfortable opening the key fob, remove the circuitboard and use a multimeter to check that the diode is working correctly. If you're not sure with this, you can go to your local Oreilly or hardware store and utilize their RF frequency tester. This will let you know whether the key fob is sending an RF signal.
Programming
Key fobs endure many abuses and aren't completely indestructible. They may lose their connection to the receiver in your car due to shock or low battery, requiring the reprogramming. A professional auto locksmith or dealer will be able to reprogram your key fob and get it working again. If resetting or repairing your key fob fails it is possible to replace it.