I want to know if it possible turning off a car sending an electric signal, this without the switch of the car?

Maybe adding some modifications to the electrical system of the car, I want to apply this to the most simple circuit of a car that you can imagine, this is because I am planing to add some modifications to turning off the car using an Arduino with a GSM module.

Thanks in advance.

  • First question, are you planning for the Arduino as an anti-theft module or just for yourself? Commented Aug 7, 2017 at 21:56
  • Just for my self.
    – csuazo
    Commented Aug 7, 2017 at 21:58
  • Some keys have an electrinic signal built in that if the key is not present it will turn off / operate alarm anyway
    – Solar Mike
    Commented Aug 8, 2017 at 7:06
  • 1
    What car are you planning on doing this on? Commented Aug 8, 2017 at 15:36
  • 1
    Is this an antitheft thing? A power reduction thing? Safety issues? (i.e. you really don't want to shut off a car while its driving...)
    – zipzit
    Commented Aug 8, 2017 at 16:11

2 Answers 2


This depends partially on the make/model of the car, but there are several different ways depending on what your goal is.

With some newer cars, it's possible to feed data to the computer - although I really would not do that.

The best way is going to be adding a relay to one of your circuits and having the Arduino control the relay.

There are several questions you're going to have to ask yourself though:

  • Do you want it to only cut ignition (key in ACC? Or also all accessory circuits (i.e. key in OFF position)?
  • Do you want it instantly off?
  • Do you want your Arduino to also interrupt with the startup sequence?

I'm sure there are more considerations as well, but those are just a few.

I think the simplest way would be to put a normally closed relay on the ignition line and wire it to the Arduino as the control. This way when the Arduino says to, you can cut ignition for a set amount of time (1000 ms) then when the car is off, or the Arduino is not sending a "kill signal" then the relay will be closed and allow for normal operation.


Apply caution when you start messing with core electrical functions like this. If you wire things wrong, or start messing around with the cars ECU or PCM you run the risk of damaging expensive and sensitive components.

I assume since you're playing around with the Arduino in this way you're at least somewhat savvy with electronics, but you do want to be careful. Depending on the car, some computerized components can get very expensive very fast.

Additionally, there are some parts of the automotive electronics/ignition systems that can be hazardous to your bodily health too - so always be careful!


You can easily with a system of switches to replace the ignition switch or work in tandem with the ignition switch. These switches will act as your kill switch and can be controlled remotely through your Arduino.

You will need the service manual for your vehicle and to examine the wiring diagram for the ignition switch. You will add switches that allow you to control behavior of the system via the Arduino you are using to control it. It will be extremely car specific.

Something like: Set switches to match the state of off -> switches off ground connection. Set switches to match the state of acc -> switches on ground connection, acc, and constant.

I had an ignition switch go bad in one of my cars so I added external switches instead of replacing it ($5 vs. $150) but in that action made my car start-able without the key. So think through the consequences before you even correctly modify it. :)

If you are just wanting a kill switch to make your car much harder to steal, wire an on-off switch into the ignition switch ground and re-route it to a inconspicuous location. The amount of time required and need for understanding of the car to undo what you have done will defeat the average thief.

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