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Lock Blog

A resource for consumers, locksmiths, and security professionals

5 Reasons Your Car Key Fob Is Not Working After A Battery Change

by Ralph December 1, 2021

The most common solution when a car remote is not working is to change the battery. But what do you do if your key fob is not working after a battery change? The first thing you have to do is figure out what is going on.

Without knowing why a key fob is not working after a battery change, there is no way to recommend a solution. But once you find out what is wrong, you can also find your fix.

Reasons for a key fob not working after a battery change include:

  1. Worn Buttons
  2. Broken Locks
  3. Deprogramming
  4. Damaged Key
  5. Electrical Issues


How do I find out which battery my key fob uses?

To find the battery your car key fob uses, open your fob. If there is a battery inside it, there will likely be an engraving that begins with CR followed by a series of numbers. Without a battery or engraving, check your owner’s manual or look up your car’s make, model, year online.

Will changing the battery on my key fob make it work again?

The most likely reason for a key fob not working is a dead battery. That being said, there are more severe problems your keyfob may be experiencing. If you have a key fob not working after a battery change, you may need key fob replacement or even some form of car door lock repair.

How do I know if changing my key fob battery will fix my car key?

A good indication that a car key fob is not working due to a dead battery is when the key does not work in any circumstance. All buttons are equally ineffectual on all door locks. No lights flash when buttons are pressed, indicating no signal sent. However, the spare fob works perfectly.

What do I do if my key fob is not working after a battery change? 

If your key fob is not working after a battery change, before you move on to replacing car remotes, double-check that your locks are functioning properly. Also, check that you have not deprogrammed your fob accidentally.

Can you fix a key fob not working after a battery change?

Though a battery change is potentially the quickest fix when a remote is not working, it is certainly not your only available solution. Look into whether your ultimate problem lies with the key fob or the car. After finding your underlying issue, fix or replace the broken parts.

1. Worn Buttons

The buttons on a remote wearing down may be why a key fob is not working after a battery change. Buttons on a key fob use contacts that send signals to a circuit board when the button is pressed. The contacts can wear down, or the buttons can wear so they don’t touch the contacts.

The most obvious sign of a worn button is when the plastic has fallen apart and the contact is exposed. Without a visual indicator, you have to use context clues. For example with a key fob will not unlock doors, but the lock button does work, you might have a worn unlock button.

It is always a good idea to test a spare remote and see if whatever issue you are experiencing persists, even with a different key. If two key fobs have the same problem, the reason for your key fob not working after a battery change is probably not a worn button or contact issue.


  • Pressing buttons works some of the time, but not every time.
  • Buttons can work when pressed in a specific way.
  • One button works, and another does not.


  • Replace the remote housing.
  • Replace the car key fob.

2. Broken Locks

The cause of a key fob not working after a battery change might have nothing to do with the key fob. It may be that you have a car door stuck in the lock position or need to fix car door latches. In any case, the problem could be that a part of the lock has broken.

The best way to tell whether a broken lock is the source of your trouble is to check and see if the remote is working to open or lock one or more doors. Sometimes multiple door locks can fail at once, but if they start failing one by one, this is also a sign that your key is not responsible.

If a car door won’t open from the inside or outside, that is a great indication that no work needs to be done to the key fob. Locks that do not move no matter how they are manipulated are broken locks. Other than doors, you might also encounter the need for car trunk lock repair.

It is not a good idea to neglect your car door locks. If the doors are not opening properly, it is a major safety concern. And if your locks are not reliably locking, your security is going to suffer. Make sure to fix your locks as soon as damage starts to affect usability.


  • Remote will open some door locks and not others.
  • Indicator lights flash to show a signal is being sent without doors opening.
  • Door locks visibly move without fully engaging or disengaging. 
  • Locks do not open or lock with the key or when directly manipulated.


  • Car lock repair.
  • Car lock replacement.

3. Deprogramming 

With a car remote not working after a battery change, there is a chance that it was deprogrammed. Deprogramming refers to instances where the vehicle’s onboard computer has been procedurally instructed to remove all existing keys from its access list.

Deprogramming can happen as a result of buttons pressed on the remote. Certain button sequences can send a message to the onboard computer to invalidate all existing keys. If you have more than one key fob not working after a battery change, you might be experiencing deprogramming.

Some key fobs can be programmed to multiple vehicles. These keys have a sequence that changes which vehicle the fob will open. It is possible to accidentally switch your key fob into an unprogrammed secondary key state.

You can check online or in your owner’s manual to see if this is a feature your car has. If it is, check to see if you can reprogram your key yourself. Keep in mind that key fob programming may require professional tools if you do not have a spare key.


  • A vehicle has a self-deprogramming or reprogramming procedure.
  • Spare remote is also not working.
  • Key fob abruptly stopped working entirely.


  • Self programming (in limited cases)
  • Call locksmith
  • Contact dealership

4. Damaged Key

For this article, “damage” will refer to harm that has come to the key fob outside of basic wear caused by repeated instances of standard use. This type of damage can be caused by water, blunt force, circuit board scratches, etc.

You should suspect a damaged key is the reason your key fob is not working after a battery change if the fob suddenly stopped working after it was opened, stepped on, or got wet. Damage may be visible, but not in every instance.

Unlike a key with worn buttons, a damaged key will need to be fully replaced. For this reason, you are likely to incur a higher key fob replacement cost if you have a damaged key. If your issues only stem from the housing being damaged, partial replacement may be an option.


  • Problems arise after sudden damage to the key.
  • Key is visibly broken.
  • Buttons will not move.
  • A spare key works.


  • Housing replacement.
  • Full key fob replacement.

5. Electrical Issues

In more severe cases, the reason for a key fob not working after a battery change may be because of damage to the vehicle’s electrical system. This may happen after service to the car where the dashboard panels or side panels had to be removed and reinstalled.

While panels are removed, wires are exposed. They can be damaged or disconnected unknowingly during service or when the panels are being put back on. If you just had this type of work done before your key fob started acting up, check for further electrical malfunctions.

Other electrical failures that may accompany key fob issues are the car horn now working, lights not turning on, etc. Fixing this kind of problem is beyond what an auto locksmith service offers. A car mechanic has more training and supplies to solve general electrical problems.


  • Car is experiencing other electrical malfunctions.
  • Problems started after wiring was exposed, worked on, or otherwise accessed.


  • Reconnect wires.
  • Replace damaged wires.

Final Considerations

With a key fob not working after a battery change, the solutions get a bit more complex. However, you can always reduce that complexity by calling a locksmith. Mobile locksmith services enable a professional technician to come to you and solve your key fob problem.

In many cases, the simplest solution will be to replace your car key remote, but not when the issue is with the locks or the electrical system. If you have any questions or would like to share your thoughts, please leave a contact below.

Category: Automotive, Car Keys

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