Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Ignition Lock cylinder issue

The attempted theft may have caused damaged to the housing behind the steering wheel. The spring loaded action comes from inside the housing and not the lock cylinder so I have a feeling you will either have to replace the...

Q: Is a Push-Button Ignition as Reliable as a Keyed Ignition?

Keyed ignitions and push-button ignitions are vastly different, yet they work equally well. In fact, push button ignitions are becoming more of the norm. For a highly technical, electronic system to be considered more preferable to an older, less technical...

Q: My car key stop working last night and its was the only key I had. Where could I go to get a new key?

Hi there. The dealership would have a replacement key for the vehicle. First try replacing the battery in the key fob or the key it self. Then you will have to reprogram the key to the ignition and the door...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...