How does keyless entry and ignition work in your car?

Keyless entry and ignition systems in cars use wireless technology to allow drivers to unlock and start their vehicles without inserting a key into a traditional lock or ignition switch. Some systems even allow you to start the vehicle remotely, although this does pose a security risk as someone could jump in your vehicle as you approach it, and drive off.

Here’s how the system works for unlocking and starting the car:

Keyless Entry

Keyless entry is super convenient if you hate rummaging around in your pockets or bag for your car keys. You can simply walk up to your car and get in, or when you want to lock it, you push a button on the door handle and walk away. It won’t lock if the key is still in the car.

The car has a key fob that contains a small radio transmitter powered by a battery (usually a CR2025 or CR2032, or similar). When the driver approaches the car with the key fob, the car’s sensors detect the signal emitted by the fob.

Once the car recognises the signal, it checks if the fob is within a certain range (usually a few meters). If it is, the system unlocks the doors, often automatically, when the driver touches a button on the door handle, or puts their hand behind the handle.

The signal sent by the fob is encrypted to prevent hackers from copying or intercepting it, although that doesn’t stop relay theft for some car models. The car’s receiver has to decode the signal correctly to allow entry.

Keyless Ignition

Once inside the vehicle, the car again detects if the key fob is within the car’s cabin, typically by searching for its specific radio frequency signal.

Instead of turning a key in the ignition, you press a “Start” or “Ignition” button on the dashboard. The car’s system verifies the proximity of the fob and allows the engine to start.

The car’s computer verifies the unique code from the fob before enabling the engine to start. If the fob is not present or the code doesn’t match, the engine won’t start, thwarting anyone who is looking to steal your ride.

How it Works

The communication between the car and the fob is based on RFID technology. The car has antennas around its body that detect the fob’s signal, and the fob uses a unique code that the car recognises. This means that you might be able to enter the car from the boot or the passenger door, not just the driver door. In my VW Golf, if I unlock the boot without the key, as soon as I close the boot, it locks the car again, whereas it doesn’t do that with the driver’s door.

The key fob is powered by a small battery, which needs to be replaced periodically. If the battery dies, many cars have a backup system, such as an emergency key hidden inside the fob or a physical ignition slot to start the car manually. Sometimes, holding the key against a certain part of the vehicle (e.g. the steering column) can allow it to start.

Downsides

The main downside to this is a much more bulky key. You might remember a time when it was just a metal key which you could hang around your neck and go swimming. Now, keys are sensitive, and very expensive if you need to replace them. I paid $450 to replace a lost key and have it re-coded, and that was a non-genuine VW key (the genuine VW one was 50% more expensive!)

The other downside is the need to change the battery reasonably frequently – a small cost, but it adds up over the life of the car.