How to Fix a Key Fob That isn't Working
If your key fob doesn't work and you're not sure why, you can fix it with a few simple steps. The first step is to make sure it's not the backup remote.
If your backup remote cannot lock and unlock the doors of your car, then it is most likely that the primary remote isn't working. Most problems with car remote keys are caused by circuitry or battery problems.
Battery
The battery in the key fob may wear out over time. It is fairly easy to change out a battery, although it is crucial to ensure that you use the right type that you can refer to the owner's manual or talk to 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 which can damage the remote. If changing the battery doesn't solve the issue there could be other issues requiring professional attention. If buttons are broken or stuck, for example it could be necessary to take the remote apart and rework each component. It is also possible to reprogramme the vehicle to recognize the new fob.
Buttons
Through frequent use, key fobs can get dirty and worn. This is not uncommon however, it can cause buttons to cease functioning or require a difficult press to get them to work. 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 a bit of time and a few items you might already have in the house.
First, check that the batteries are correctly inserted and that the indentation on the back of the button is filled. Take the remote apart and look over the circuit board. Check for signs of corrosion or other indications that the buttons are worn out or damaged, such as missing conductive paint. Utilizing a Q-tip dipped in rubbing alcohol, gently clean any membrane contacts that have damaged or have conductive paint missing. Don't rub too hard as this can damage the conductive paint and prevent the button from firing when pressed.
Also, carefully check the battery connector terminals for an unattached solder connection. If this is the case, simply reconnecting them may restore functionality to the button. You can use the same method to restore functionality to any other loose connection inside the fob.
If, for instance, any of the buttons made of rubber that are on the front of the key fob aren't functioning or require a hard press to work it is likely that the graphite disks on the back of the button are deteriorating and require replacement. This can be done by rubbing a pencil across the disks, which will bring the button back to its original state.
If none of this is helpful, or if the button doesn't respond to a hard push, then it may be that the circuit board has gone bad. It is possible to fix the issue by cleaning and re-soldering your fob however, you should have a spare in case it doesn't work.
Circuitry
The circuit board in your remote control may be dirty, regardless of whether the buttons on the key fob function or not. A very thorough inspection will usually resolve this problem. Broken and damaged cases are the most common causes of dirty boards. A broken case can let water and other debris to get into the circuit board, causing it to short out. Water can also get through pins and vias, which are tiny connectors found on the board.
If you're handy enough to remove your key fob, and you're not afraid of some mess, we can take off the buttons and solder new ones in their place. Also, it's worth checking the connections between the battery terminals. If they're loose, the buttons might not work or even become stuck in their down position. Soldering the terminals and buttons back in their place is generally all that's required to return keys that are not in working condition.
Non-Remote transponder chips
The non-remote chips that are sealed are more durable than their remote fobs. However, remote car key repair are susceptible to cracking when a hole is made into 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 chip failures.
If you're handy enough to remove a sealed non-remote key fob and are able to bear the mess, you can easily remove the circuit board and test the fuse with a multimeter for proper diode function. If you're not comfortable doing this, head to your local hardware store or Oreilly's, and they will usually have an RFID frequency tester that can determine whether the key fob transmitting a signal.
Programming
Key fobs aren't impervious to destruction and are susceptible to being damaged by a variety of factors. They may lose their connection to the receiver in your car due to shock or a low battery, requiring the reprogramming. A professional auto locksmith or main dealer can reprogram your key fob to get it working again. If resetting or fixing the keyfob is not working, you may need to replace it.