Q: How do Keyless Push-Button Start Systems Work?

asked by on November 19, 2015

How do keyless push-button start systems work?

Keyless push-button starting systems are advanced electronic systems that utilize wireless and wired communications to communicate passive anti-theft information and engine starting permissions between several control modules (computers).

The first item in these systems are the keys, which are not really keys at all. These key fobs are actually transceivers. They have an electronic chip in them called RFID (radio frequency identification) chips. Every RFID chip has a unique identification code that is programmed into the control module that operates the passive anti-theft system. These ID codes help to ensure that you are the only person who can gain entry to your vehicle or start the engine.

There are sensors in each door handle that, when you grab one, send a voltage signal to the anti-theft module requesting the doors to be unlocked. The anti-theft module sends a message via antennas in the front doors to the RFID chip inside the key fob. The RFID chip then transmits its ID code back to the anti-theft module where the code is checked against the programmed codes in the module. If the key code is recognized, the anti-theft module then communicates to another control module via a wired network and commands the door locks to be unlocked.

To start the engine, the same basic procedure is followed with a few minor differences.

When you push the Start/Stop button, the button sends a voltage signal to several control modules, including the anti-theft module and the powertrain control module (PCM). The anti-theft module sends another message to the RFID chip via antennas inside the vehicle. The key fob transmits the chip ID code to the anti-theft module who, once again, verifies the key code against the code programmed into the module. Once the code is accepted, the anti-theft module communicates to the PCM, allowing the PCM to enable the starting system, ignition system, and fuel injection system. The starter motor is engaged and the engine should start.

There is one crucial point to remember about these systems, however. The key fob must be inside the vehicle for the engine to start. If the engine is already running and you get out of the vehicle, the engine will continue to run until the fuel tank runs empty. After the engine has been shut off, the engine will not restart if the key is not inside the vehicle. So when your spouse drops you off at the airport, please make sure that you gave them the key to the car. Being stranded at the gas station without your car key can be a little embarrassing.

If your vehicle won’t start, feel free to reach out to a professional mechanic. Whether it’s a mechanical issue or an electronic one, we’ll help your car get “started” and on the road to recovery.

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