Smart Key or Keyless Entry - How It Works in Vehicles

Keyless Entry, or Passive Entry, is terminology for a system that locks and unlocks a vehicle without using a traditional key and/or pressing buttons on a Remote/Smart Key. However, Keyless Entry does NOT mean ‘no key.’ Instead, it means there’s NO need to physically insert a traditional (metal) key into the lock/ignition, as was the case in previous-generation cars.

When you enter the vehicle with Keyless Entry/Smart Key, you can start/stop the engine without actually inserting the car key into the ignition. The Smart Key’s built-in transceiver identifies the vehicle it’s ‘associated’ with and automatically activates the ignition. As a safety measure, the vehicle can’t be locked as long as the Smart Key remains inside it.

What Is a Smart Key?

A Smart Key is a sophisticated, ‘computerized’ key that electronically accesses and unlocks the vehicle’s locking system. It replaces the traditional/metal key in today’s cars. While Siemens developed the electronic Smart Key system in the 1990s, Mercedes-Benz was the first to use it in 1998 on the S-Class, under the trade name “Keyless Go.”

With the Smart Key held in a pocket, the driver can lock/unlock the vehicle and start it. The vehicle identifies its own Smart Key from the radio pulse generator in the key fob, which detects the radio signal via one of many antennas placed around the vehicle.

With the smart key system, the vehicle can be unlocked by pressing a button or sensor built into the door handle. Additionally, the Smart Key system comes with a Start-Stop switch. If the Smart Key is lost, you can unlock the car using a spare key blade (without an electronic circuit) provided by the manufacturer.

Button-Equipped Door Handle (Image by Mercedes-Benz)

The smart key can unlock the immobilizer and turn on the ignition without inserting the key into the ignition, as long as it remains inside the car. When you get into the vehicle with the Smart Key in your pocket, all you need to do is press the Start-Stop button to start the engine.

Ways to Lock Your Vehicle While Keeping the Smart Key in Your Pocket

Pressing a button on the door handle, OR
Touching a capacitive area on the door handle, OR
Walking away from the vehicle

In some advanced versions, the system automatically adjusts settings to match the end user — the person operating the Smart Key to unlock the car. It can also remember user preferences: seat and steering wheel positions, exterior mirror settings, cabin climate temperature, music system and volume levels, etc. In some more advanced options, you can even customize another Smart Key to restrict the vehicle’s preset speed.