How to Fix a Key Fob That isn't Working
If your key fob won't work, you can fix it by following just a few steps. The first step is to be sure that it's not your backup remote.
If your backup remote can unlock and lock the doors of your car, it is likely that the primary remote isn't working. The majority of car remote key malfunctions are caused by circuitry or battery problems.
Battery
It is not unusual to find a battery on the key fob for cars to degrade. It is easy to replace the battery. However it is essential that you use the correct type. You can check your owner's guide or contact the manufacturer to determine the right type. car keying repair is also a good idea to examine the battery compartment with care because dead batteries can leak caustic chemicals that can cause damage to the remote. If replacing the batteries doesn't solve the problem, it may be that there are other issues that require professional attention. If the buttons are damaged or stuck for instance it could be necessary to remove the remote and rebuild each component. You can also try reprogramming your car to recognize the new key fob.
Buttons
Key fobs can become dirty and worn out from frequent use. It is not common for buttons to stop working, or to require a long press to get them working. This can be a huge hassle, especially if you are away from home and you need to start your vehicle. Even malfunctioning or worn-out buttons are often fixable with a bit of time and materials you already have at home.
First, check that the batteries are properly inserted and that the indentation at the back of the button has been filled. Then, carefully remove the remote and examine the circuit board. Check for signs of corrosion or other signs that the buttons are worn or damaged, like missing paint that is conductive. Use a Q-tip, dipped in rubbing alcohol to gently clean any membrane contact that has become damaged or where conductive painting is missing. Avoid rubbing too hard since this could cause damage to the conductive painting and prevent the button firing when pressed.
Also, make sure to inspect the battery connector's terminals to ensure any loose solder connections. If this is the case, soldering them back in place may restore functionality to the button. The same method can be used to restore function to any other loose connections within the fob.
Finally, if any of the buttons made of rubber on the front of the key fob stop functioning or require a difficult press to function, it is likely that the graphite disks that are on the back of the button are wearing out and require replacement. This can usually be done by rubbing a pencil on the disks, which will bring the button back to its original state.
If none of these solutions work, or if you still cannot get the button to respond when pressed hard, it could be that the circuitry has failed. It is possible to fix this issue by cleaning and re-soldering the button but you should also have a spare in case it doesn't work.
Circuitry
The circuit board of the remote control could be dirty, regardless of whether the buttons on the key fob function or not. The issue can be solved by a thorough inspection. The most common causes for dirty circuit boards are water and damaged cases. A damaged case can allow water and other debris to enter and short circuit the electronics. Water can also eat away at pins and small connectors on the board called via's.
If you are handy enough to open your key fob and you don't mind making an mess, you can take the buttons out of their sockets and put in new ones. Also, you should check the connections between battery terminals. If they are loose, the buttons could not function properly or become stuck in their down position. Soldering the terminals, and putting the button back into place is typically all that's required to return the key fob that is not working to working order.
Non-Remote transponder chips
Sealed non-remote transponder chip are more durable than remote fobs they are contained in, but they can be cracked by a hole drilled into them or run over by a lawnmower or door handle for a car. Failures of the fuse are typically the cause of non-remote chip failures.
If you are not comfortable opening the key fob, you can remove the circuitboard and use a multimeter to determine if the diode is operating correctly. If you're not comfortable doing this, go to your local hardware store or the Oreilly's and they usually have a radio frequency tester that can determine if the key fob is transmitting a signal.
Programming
Key fobs aren't impervious to destruction and are susceptible to damage by a variety of factors. They can lose their pairing to the car's receiver due to shock or low battery, requiring them to be reprogrammed. A professional auto locksmith or main dealer will be able to reprogram your key fob and get it working again. If resetting or replacing your keyfob does not work it may be necessary to replace it.