Skip the auto shop - Our mechanics make house calls

Q: How Does a Keyless Push-Button Ignition Work?

asked by on

How does a keyless push-button ignition work?

A: Push-button ignition system designs are hig...

Push-button ignition system designs are highly technical and vary between manufacturers. Here, in a nutshell, is how they work.

When you push the “engine start” button, that button sends an electrical command (voltage signal) to several control modules (computers). One control module (we’ll call it the body control module) uses antennas located inside your vehicle and sends out a radio signal to the key in your pocket. This reaction wakes up the RFID chip inside the key, and asks it to identify itself. The RFID chip in the key responds to the ID request with a radio message of its own where it sends its ID code back to the body control module.

The other control module that received the “engine start” command is the engine computer. We’ll call it the powertrain control module (PCM). The PCM is ready to start the engine, but it needs information from the BCM first, since the BCM controls the keyless entry system of the vehicle.

If the BCM accepts the RFID code from the key, it communicates this to the PCM, and the engine start is enabled. If an unprogrammed key is used, the BCM rejects the key code. The reject notice is communicated from the BCM to the PCM and the engine start is disabled. All of this communication occurs in less than 1/2 second!

This same process occurs to automatically unlock the doors of your vehicle whenever you grab a door handle.

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

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: How does the Intelligent Key function as a remote keyless entry device?

While the Intelligent Key will let you open the doors and the trunk without having to press a button on the key itself, it does double as a remote entry device. To use it, you just need to take the...

Q: car won't start.

When a vehicle will not start it needs three things. It needs proper air/fuel mix and compression then ignition to ignite the mixture. If any one is missing or is not correct, it will not start and run. With this...

Q: Cranks great will not fire up - 1992 Mazda 929

The antenna wire should not be connected to anything that would cause the car to not start, especially if it is getting power to crank. I would suggest checking to see if the spark plugs are getting fuel to them....

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control 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...