How to Fix a Key Fob That isn't Working
If your key fob won't work then you can fix it by following some simple steps. First, check to make sure it's not your backup remote.
If the backup is able to lock and unlock your car doors, then there is likely an issue with the main remote. Most problems with car remote keys result from battery or circuitry problems.
Battery
The battery in the key fob may get worn out over the course of time. It is easy to replace batteries. However, it is important to select the right type. You can check your owner's manual or call the manufacturer to find out the correct type. It is also essential to inspect the battery compartment, since dead batteries can leak caustic chemicals that can harm the remote. If changing the battery doesn't fix the problem there could be other issues requiring professional attention. For example, if buttons appear stuck or damaged, it may be necessary to take the remote apart and rework its components. You could also try reprogramming the vehicle to recognize the new fob.
Buttons
Key fobs can become dirty and worn-out from repeated use. It is not uncommon for buttons to cease functioning, or require a hard push to make them work. This can be very frustrating particularly when you're away from home and have to switch on your car. Fortunately, even worn out or malfunctioning buttons can often be fixed with just a bit of time and some of the materials you have in the home.
First, check that the batteries are properly charged and that the indentation on the back of the button is filled. Open the remote carefully and inspect the circuit board. Look for signs of corrosion or other signs that the buttons are worn out or damaged, such as missing the conductive paint. Use a Q-tip dipped in alcohol, gently clean any membrane contacts that are worn or where conductive paint is missing. Don't rub too hard as this can damage the conductive paint and prevent the button from firing when it is pressed.
Check the battery connector's terminals carefully for any loose solder connections. Soldering them back in place will allow the button to function again If this is the situation. You can apply 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 have stopped working or require a difficult press to function it is likely that the graphite disks on the back of the button are wearing down and need to be replaced. This can be done by rubbing a pencil over the disks, which will bring the button back to working.
If all of this doesn't help, or if the button still does not respond to a hard press It could be the case that the circuit board itself has gone bad. This can be fixed by a quick clean, and replacing the solder, but it is best to have an extra fob on hand in the event that this method fails for you.
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If the key fob buttons function, the circuit board inside your remote may be dirty. A very thorough inspection is often enough to resolve this problem. The most common causes for dirty circuit boards is water and damaged cases. A damaged case can allow water and other debris to get into the circuit board, which can cause it to short. Water can also get through pins and vias, which are tiny connectors found on the board.
If you are handy enough to open your key fob and don't mind making a mess, we can take the buttons out of their sockets and then solder new ones. Also, it's worth checking the connections between battery terminals. If they are loose, the buttons may not function properly or become stuck in their down position. Soldering the terminals and buttons to their original positions is often enough to restore a non-working fob to working.
Non-Remote transponder chips
The non-remote chips that are sealed are more durable than remote fobs. However, they are susceptible to breaking in the event of a hole being drilled in them, or if a car door handle or lawnmowers is pushed over them. The failure of the fuse is usually to blame for non-remote chips failures.
If you're able to open up a sealed non-remote key fob and are willing to put up with the mess, you can remove the circuit board and examine the fuse using an instrument to verify diode function. If you're not comfortable with this, you can go to your local Oreilly or hardware store and use their RF frequency tester. This will inform you whether the key fob is sending a signal.
Programming
Key fobs aren't impervious to destruction and can be damaged through a variety of causes. They can lose their pairing to the receiver in your car because of shock or a low battery, requiring them to be reprogrammed. A professional auto locksmith or a main dealer can reprogram your key fob to get it back up and running. If resetting or replacing your key fob fails it may be necessary to replace it.