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How to Replace the Battery in Your Car's Remote Control Key

Tom Lohr is an avid home DIY enthusiast. He prefers to spend the money he saves on new tools and gardening supplies.

Your trusty key. What would you do without it?

Your trusty key. What would you do without it?

It WILL Happen to You

It always happens at the worst time; you try to unlock your car using the remote control function on your key and nothing happens. Normally, this happens either in the rain or when you have two arms full of groceries. Or perhaps like me, when leaving at 4am to get an early start on a 1,700 mile road trip.

It's not the end of the world, you can always unlock your car by inserting the key into the slot on the door. We did that for decades and it was no big deal. But in the 21st century, it seems we can't be bothered with using the old school method. Your car may not start without a functioning electronic key.

You can do two things when it finally happens: take it to someone to have it replaced (and pay out the nose), or perform this simple task by yourself and save money and time and avoid the hassle of having to take it to someone. These simple steps will get your remote control key up and running in just a few minutes.

Typical key battery. The number type is on the battery itself.

Typical key battery. The number type is on the battery itself.

Avoid It Becoming an Emergency

An ounce of prevention is worth a pound of cure. I'm not sure who said that, but in this case it's true.

Like all battery operated devices, your key just doesn't die suddenly; it becomes weaker and weaker until it finally does give up the ghost. If you notice that you have to be closer to your car for your key to work, that's battery's way of telling you that the end is near. To avoid having no remote function at all, replace that battery as soon as you notice the key is experiencing diminished performance.

Note the TINY screw just above my thumb.

Note the TINY screw just above my thumb.

Get a New Battery

Your owner's manual or other documentation might tell you what kind of battery you need. But in most cases, you are going to have to open the key twice. Once to get the proper battery number, and another time to actually replace it. Don't think you can just jet out to the local department store and pick a new one up. In some cases you might be able to, but in many instances it is some oddball battery number that you have to order. Be proactive.

Prying the halves apart with a butter knife (after removing the screw).

Prying the halves apart with a butter knife (after removing the screw).

Open the Key

Take a good look at all of your key before trying to open it. Some just pry apart, but some are also held together by a tiny screw. Determine if you have to remove any screws before separating it in half. If your model does have a screw (or screws) remove it/them. After, locate the small slot on the side of the key that will be in the middle of the line that separates the two halves. You can use many things to pry the halves apart, just don't use anything sharp as it will damage the key. I prefer to use a butter knife.

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The halves separate easily.

The halves separate easily.

Remove the Battery

Once the key is apart, one half will have some electronics in it, the other half will house the battery. Remove the clip that holds the battery in place. This is where you will find the battery number if you are performing this step to get the battery information. If you already have a new battery, note the positive/negative orientation of the battery and then remove it.

Key open. Holding clip still on the battery.

Key open. Holding clip still on the battery.

Install the New Battery

This step is as simple as it seems. Plop the new battery into place using the same positive/negative orientation as the old one. Replace the holding clip.

Key opened. Electronics on one side, battery on the other.

Key opened. Electronics on one side, battery on the other.

Reassemble the Key

Place the two key halves together. They will snap together. Depending on your key model, this may be all you need to do. If you removed any screws, replace them.

Test Your Key

Get within ten feet of your vehicle and test the remote function on your key. Hopefully, it will lock and unlock as it should. If not, your key lost its electronic coding and will need to be reset. This will happen if your key battery has been dead for some time. There won't be enough power to retain the electronic coding. Don't worry, you can reset it yourself.

Reset Your Key Coding

If your key with a new battery still doesn't work, you will need to reset the coding. This procedure will be slightly different for each make of vehicle. It is unlikely to be found in the owner's manual (because they want you to let them do it for a hefty price) but you can find the procedure on the web for sure. The following is how it is reset for a Honda. Again, the procedure for your key may be slightly different.

  1. Get into the vehicle and close all the doors and keep them unlocked.
  2. Turn the key to the “on” position. This is one stop before the engine would actually start.
  3. Within 5 seconds of turning the key to the “on” position, press the lock button on your key for 1 second.
  4. Turn the key to the “off” position.
  5. Repeat the previous steps 2 and 3 twice for a total of 3 times. Each time must be within 5 seconds of the previous time.
  6. Turn the key back to the “on” position and leave it there.
  7. Press the key's “lock” button. You will hear the locks on your car activate, but that is actually your car reprograming your key. Keep the key in the “on” position.
  8. Give it about 30 seconds to complete programing and then remove you key.
  9. Test your key's lock/unlock function (your key will not lock or unlock if it is still in the ignition).


Your key: slightly worn, but good as new.

Your key: slightly worn, but good as new.

Welcome Back to the 21st Century

See, that was easy. Think of all of the money you saved. And don't let this happen again.

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