Electronic keys are handy and protect your vehicle from thieves. Fortunately, many of these keys and key fobs can be replaced and programmed at home. To program a car key, turn the ignition on and off with working keys. Then use the unprogrammed key or press a button on the key fob. Your key should work perfectly, but if it doesn't, take it to a professional car dealer or locksmith.
Steps
Method 1 of 3: Programming a car key

Step 1. Sit in the driver's seat
You must have access to the car's ignition to link the keys to the car's systems. You may need two working keys to make or repair a third. Please refer to your vehicle manual for additional steps required by the manufacturer.
- Also search online for the make and model of your car. You can find the exact steps needed to program keys for your car.
- Many newer cars have improved transponders in electronic keys. These must be programmed by a dealer or car locksmith, for the specific anti-theft system of your car.

Step 2. Insert a programmed key into the ignition
Insert the key into the slot and leave it alone for a while. Put the other two keys where you can easily reach them. You have to be quick to activate the car's programming mode. Make sure you know which key is which.

Step 3. Turn the car engine on and off
Turn the key you placed in the ignition. Do not start the engine. Simply turn the key to the on position, which activates the electrical system. Immediately turn the key back so that the car turns off.

Step 4. Turn the car on and off with the second working key
You have about five seconds to remove the first key. Have the second programmed key ready and put it in the ignition. Turn the key again so that the car turns on without starting the engine. Turn the key back so that the car turns off.

Step 5. Insert the third key and turn it
You have about ten seconds to replace the second key with the unprogrammed key. Quickly turn the key to the on position one more time. A second later, turn it back to the off position. Leave the key in the ignition.

Step 6. Wait for the security light to illuminate
Look on your dashboard for the car's safety light. It should stay lit for about three seconds. It may be necessary to press the buttons on the key you wish to program. When you're done, remove the key and test it.
Method 2 of 3: Programming a key fob

Step 1. Turn on the ignition
Sit in the driver's seat with the ignition key and key fob (also known as 'keyless entry remote'). Close all car doors. Place the key in the ignition and turn it to the on position. Do not start the engine.
Consult your owner's manual or look online for specific steps for your vehicle. Different manufacturers require slightly different steps to complete the reprogramming process

Step 2. Press the lock button on your remote
Point the remote at the receiver if you know where it is. It will be located somewhere at the front of the car, such as above the mirror, so point it forward. Press the lock button within a few seconds of turning the key.

Step 3. Turn off the ignition
Immediately reach for the key in the ignition. Turn off the car. Keep moving fast. You only have a few seconds before the car's system resets the commands.

Step 4. Repeat programming with other remotes
Many cars desync all remotes if you try to program a new one. Start at the beginning. Turn on the ignition, press the lock button on the next remote, and turn off the ignition. Do not wait between actions.
- Each key must be reprogrammed immediately after the previous one. If you wait longer than a few seconds, the car will exit programming mode. You will have to start over if you want to program all the remotes.
- Some cars require you to repeat the cycle several times to get into programming mode. You can hear the locks click to indicate success.

Step 5. Turn on the ignition
Turn the key in the ignition again. Turn on the car, which activates the electrical system. Do not start the engine.

Step 6. Press the lock button on the first remote
When you press the button, the car should enter programming mode if it wasn't already. The car's locks are activated to indicate that this has happened.

Step 7. Press the lock buttons on all remotes
Start with the first remote and press it again to make sure it's programmed. The locks should sound, indicating that the remote has been successfully programmed. Quickly move to the next remote. Repeat this process for each remote you want to program. Then you can switch off the ignition and test your remotes.
Method 3 of 3: Replacing keys

Step 1. Make sure you have an empty key
Empty keys can be ordered fairly cheaply online. Make sure you get keys specific to your make and model of car. The keys must also be empty. For example, you can't take a remote for your old car and program it for your new car, even if they are the same make and model.
With newer cars you probably won't be able to program a new key yourself. You will need to go to a dealer or locksmith

Step 2. Call a locksmith or dealer
Electronic keys all have transponder chips. Some let you unlock the car but not start it. You will need to call a certified dealer from your automaker or a locksmith. Both can help you when you can't program your key.
- These professionals will use your vehicle's Vehicle Identification Number (VIN) to ensure you get the correct key.
- The VIN number can be found on most official documents, including the vehicle title, registration and insurance card. You can also find it on the right side of the dashboard on the windshield.

Step 3. Bring your property information to the locksmith
By law, you must show your driver's license and registration when ordering an official key. This is to prevent someone from taking your car and getting a new key. You can also find a code card in your car manual. Take these with you to make key making easier.
Tips
- The steps for programming keys differ from manufacturer to manufacturer. Consult your car owner's manual or search online for your car make and model to find the specific steps.
- It's a good idea to keep several working keys handy. Some car brands require you to have two working keys before you can program a new one.