Key Fobs for Cars: How They Work and How to Maintain Them

Key fobs are highly convenient, giving you easy access when you have your hands full. Some key fobs even start your car, activate the windows, adjust your seat or send out a panic alarm in an emergency. Wondering how your key fob works and whether it’s secure? Here’s a primer on key fob technology.

Radiofrequency (RF) Technology

Key fobs work on radiofrequency technology. When you press a button on the key fob, it sends a data stream to the car by an RF transmitter. Generally, you need to be within a few yards of your car for the system to receive the command. This data stream tells the car what you want it to do. The receiver reads the data stream and sends the command to the appropriate module. In some cars, you don’t even need to press a key fob. You just get near your car and the doors unlock or the engine starts when you touch a button on the dashboard. The car recognizes the driver through the key fob.

Problems With Key Fobs

Key fobs make it easier to keep up with your “car keys,” but the technology isn’t perfect. The technology can be hacked to capture the signal from the fob to potentially steal the car. You should check with your dealer for software updates that increase security. You should also turn off your fob at night if possible. The receiver probably has a sleep mode to reduce battery consumption, but it wakes up quickly when the transmitter sends it a signal. Even if your car is protected against theft with a key fob, you may still want to use a locking gas cap to prevent theft of your gas.

Replacement and Reprogramming

The transmitter and receiver must be synchronized, so that the codes that are sent and received are recognized. The transmitter uses rolling codes as a security measure, so each time the key fob is pressed, it sends a different code. When you press the key fob when you aren’t near your car, it picks a new code the next time it gets near the receiver. Fortunately, the receiver remembers about 250 codes from the transmitter, so the receiver still accepts the code. If you do press the button more than the allotted times, the transmitter won’t work any longer. The transmitter and receiver become desynchronized. You will need to reprogram it according to the manufacturer’s instructions. Usually, this means that you have to turn the ignition key on and off a set number of times in a short time frame to switch the car into programming mode. The transmitters will need to be pressed near the car so that it recognizes them. Then, you’ll turn the ignition off. Your key fob and receiver should now be in sync again.

You may have to go to an authorized dealer to get a replacement key fob if you lose yours. But get your headlights and other parts from an auto parts store. Check with your insurance company to see if they will cover your replacement costs.