There are eight main reasons why a key fob will not unlock doors. They break down into two categories: remote or lock problems. Once you figure out what type of issue you are experiencing, you can find the fix that will work for you.

When a key fob will not unlock doors, diagnosis and repair are often best left to a professional. But feel free to use the following information to attempt the work yourself. The information can only be general as each car and lock issue has almost limitless servicing permutations.

The most common reasons a car key fob will not unlock doors are:

• Battery
• Buttons
• Deprogramming
• Blockage
• Disconnects
• Wiring

WHY YOUR CAR KEY IS NOT WORKING

Now that we have brushed over some of the differences in car keys, let’s dive right into some of the reasons why your car key might not be working. Keep in mind that if your car key is broken, or if you broke your car key off in the lock, the points below will not help you. Let’s begin:

1. DAMAGED CAR LOCK

If your car key is not working when you attempt to unlock your car, there is a possibility that the lock itself is damaged. This could be the case even if you are not using the keyways on your car locks (i.e. opening car doors with remotes/fobs). Two main parts of a car door lock brake: the lock cylinder and the lock assembly.

You can tell which part of the car lock is broken with a bit of trial and error. Insert your key, and see if it turns. If it turns without opening the lock, there is likely something wrong with the lock assembly. If you use a working key fob to open a door, but the key will not open that same door, there is a good chance that the problem lies with the lock cylinder.

Locks can also be blocked by dirt and debris. In extreme temperatures, a car door lock can also freeze. And if you have been in a collision, the lock might be damaged due to the impact. These issues are not the result of normal wear and tear and can affect new car locks just as easily as classic car locks.

Signs of a damaged car lock

• The keyway is blocked or obstructed (you cannot fully insert the key).
• The key will open one lock but not another.
• Key will turn but the lock will not open.

2. DAMAGED KEY

One of the main reasons why your car key might not be working is simply because the car key is damaged. When most people think of damaged keys, they tend to conjure up a picture of a broken key that is split into pieces. However, a damaged key is not always visibly broken. The grooves in a key might be worn down. With the improper depth on one or more of these grooves, the car key will no longer match the internal mechanisms of the lock or the ignition.

Keys are physical components, which means that each of these elements is prone to some wear and tear over time. Most people do not pay enough attention to their locks and keys to realize the effect that constant use might have on them. Coupled with a lack of maintenance, it increases the probability of keys being damaged. Simply duplicating an existing car key will result in a copy of your existing issue.

Signs of a damaged car key

• The key does not open any lock or start the car.
• The locks can be opened through other means.
• A new key or lightly used spare key functions properly.

3. FAULTY IGNITION CYLINDER

Your key is not only associated with your external car door locks, but it is also the tool that works in conjunction with the ignition. Car keys are not meant to exist alone. This means that for every key that exists, there is a lock or a mechanism that it is meant to function with. If your car key does not work when it is inserted into the ignition, it does not necessarily mean that your car key is faulty or damaged.

Sometimes, this is a symptom of a much larger issue, which might be damage to your car’s ignition. If you have not realized by now, cars are moving mechanical components. (Back in the day this would be called magic, but we can call it science and technology.) The point is, mechanical components are prone to wear and tear, so it is common for things to break down, and your ignition cylinder is no exception.

Signs of a faulty ignition cylinder

• The key will open your car door but the car won’t start.
• Your immobilizer indicator light has turned on.

4. WORN OUT KEY FOB BATTERIES

Another reason that your car keys might not be working might be because the batteries in your key fob or keyless entry remote are out of juice. This is a common problem, but one that has a rather easy solution. Batteries run out after a certain period of time, so diagnosing this problem is relatively simple.

If you notice that your vehicle is not responding to the commands and signals being sent from your key fob, it is very likely the batteries are dead. However, you should keep in mind that this is not the only reason your key fob might not be working. When you do realize that your car key is not working because of worn out key fob batteries, the simple solution is to find the right batteries and then replace them. Once this is done, your car key fob should be as good as new.

Signs of worn out key fob batteries

• Key fob works sometimes but not others.
• Buttons on the car key fob must be pressed multiple times.
• Car key fob no longer works from the distance it had previously.

5. INTERNAL DAMAGE TO KEY FOB/KEYLESS ENTRY REMOTE

As I mentioned earlier, there are several different types of keys that each have their unique uses and traits. The key fob depends on communication between a transmitter and a receiver, so if one of these components is damaged, it means that your car key will not work the way it was intended. If there is something wrong with the internal electronics of your car, or if there is damage to either the receiver or transmitter, your car key will not work.

Sometimes these elements can be damaged over time and manifest in the form of frayed wires etc. In other cases, damaged internal wiring can be a result of external damage to your key fob or to your car itself. This could arise from something as simple as dropping your car keys and knocking the internal components of your fob out of alignment.

Similar to traditional keys, electronic keys can also wear down. The repeated pressing of buttons can wear down components. If you notice that one button works and not others, then the key fob could be damaged. For example, perhaps the car will unlock with the remote, but not lock. This can be taken as an indication that internal damage has occurred.

Signs of internally damaged key fobs

• The key fob has been submerged in water.
• Your car key fob has been struck or placed under extreme pressure.
• Buttons no longer depress, click, and/or are loose.

6. THE KEY HAS NOT BEEN PROGRAMMED

Traditional keys do not have a programming issue, as it is something that only keyless entry remotes and transponder keys have to deal with. If your car key is not working with your vehicle, there is a chance that the key has not yet been programmed to work with your car.

Car key programming issues are a common occurrence among people who replace their car key remotes or acquire duplicate car keys. They often forget that the transponder key and the key fob have to be programmed to communicate with your car. If you do not do this, the most you will be able to do with said key is unlock your car doors and your trunk.

Previously functioning car remotes, transponder keys, etc. might also stop working simultaneously. This is often due to security measures in modern automobiles resetting after the vehicle’s battery is changed. If you have already changed the batteries in your key fob, this could be the issue you are facing.

Signs a car key has not been programmed

• The immobilizer light turns on when the key is in ignition.
• A key fob with new batteries does not unlock/lock the car.
• You have recently changed the car’s battery.

7. AFTERMARKET CAR KEYS

Aftermarket car keys are essentially a much cheaper option that people often explore when they are looking to get replacement keys or spare car keys. You must understand the dangers that aftermarket electronic car keys can pose, but if your car key is not working, that is probably the last thing on your mind.

If you buy an aftermarket car key for your vehicle, and you neglect to reprogram it, you will most likely find that your car key is not working. Aftermarket items are usually the best place to get spare parts and other assorted automotive goods. However, you should keep in mind that most of these parts might not have been designed for your specific vehicle, so some additional work might have to be done. This is the reason why you should always make sure that your aftermarket car key is appropriately programmed and paired to your vehicle.

Signs of a defective aftermarket car key 

• The key never worked.
• The new car key is visibly different from the original.
• The key cannot be programmed.

8. YOU MIGHT BE USING A COPIED KEY

Car key duplicates are popular among drivers and for good reason. It gives you peace of mind knowing that your chances of being stuck in a car lockout are slimmer, simply because you have spare keys that you can utilize. It also gives you the luxury of being able to share your vehicle with members of your immediate family etc. However, many people do not realize that every consecutive car key duplication reduces in fidelity.

Each time that a key gets duplicated, bits of information are lost in the transfer. This means that if you duplicate a duplicate car key, the version you are going to get will be different than the original. A poorly copied key can have issues right off the bat, but a copy of a copy of a copy is even more problematic.

In some scenarios, you will find that your car key is not working, simply because you might be using a duplicate car key that does not function the same as your original key. Obtaining a duplicate car key is a much cheaper option than getting a new key cut to code, but it is not always the best option, nor is it the most secure.

Signs you are using a poorly copied key

• This is one of many key copies you have made.
• The key was not copied by a professional.
• The new car key works worse than the old car key.

FINAL THOUGHTS

Car keys are an integral part of any drivers daily activities, so whenever your car key is not working, it can be a costly hassle. Taking the time to read through the points listed out above will help you properly diagnose the reason why your car key is not working. Hopefully, this will help you find the solution fairly quickly.