How to start your car from your phone?

How to start your car from your phone?


In this article I will show you how to start your car from your cell phone. I already had a car starter installed in my truck years ago but the range was terrible and you had to press the button for a precise amount of time, otherwise it would just ignore it. So instead of pressing a button all day long from 10 feet away I decided I wanted to start my truck from anywhere in the world! I built this a few years ago, and some newer products have come out that integrate cell phones with vehicles, but this still works for older vehicles, and can also be adapted to many other kinds of appliances as well.

This isn’t just limited to vehicles. Many DIY types have attached these to their cabin’s furnace, aircraft pre-heaters, irrigation pumps on farms, servers, routers, and all sorts of other appliances and electronics.

Parts required:


-GSM activated relay. This device will contain a SIM chip that can connect to the GSM cell phone network. It’s relays must be able to be activated by phone call or text message. In my first build I used a GSM-AUTO, but found a cheaper alternative on eBay for the Quad Band version (North America) or the Dual Band (Europe, Asia, etc.). it costs around $150 which has 7 relays. Another alternative is to purchase from the online store called Relay Supply. One relay is controlled by phone call and the rest are activated by text message. The relays can be set as either momentary or latched.

-Car Starter Key Fob (the remote control thing on your keychain).

-12V DC cigarette power cord

-Small plastic bag or ESD bag.

-A few wires.


-A few screw drivers
-Soldering Iron

Step 1:

Begin with canabalizing the key fob. Instead of consuming one of my existing remotes, I turned to eBay. I found the model number of mine on the back. Its an Auto Start 05-A433. I entered this in on eBay and up popped a bunch of used key fobs that are compatible with my system. WARNING: Some of these remotes may look exactly like the one you want but they come in many revisions. Some revisions are not compatible with others. If you are not sure which to buy on eBay, try buying one new online.

You will have to sync your remote with your car starter. As all car starters and car starter installations are different, I won’t go into detail on how to do this. Whoever installed your car starter can usually do it for a fee but I strongly recommend you Google for the models manual as its a rather simple process. It usually involves either depressing the hood pin in a particular fashion (a pin that detects if your hood is popped), or pressing a button on the side of the remote starters brain under your dash.

Now remove any screws from the case and pry it apart. The circuit inside and battery are not secured in any way and came out easily.

Step 2:

Find the button that corresponds to the “start” button on your remote. Some remotes can require a combination of buttons to be pressed in a certain order, or multiple buttons pressed at the same time. This can be accomplished by soldering up two connections that are both wired through the relay (for multiple button presses) or a capacitor can be added to time delay one of buttons.

The contact in the center of this picture is already powered. When a user pushes the button, the connection is made between the interlocking contacts (they look like interlocking letter E’s) and the starter signal is sent. We will be soldering one wire to each corner of the contact. This takes a great deal of precision to ensure that you do not join the two contacts.

Step 3:

Next, solder a wire onto each connector that supplies power to the remote. Color coding the wires is a good idea. This remote takes a small but powerful 12V battery. Note that if your remote can not handle this high of voltage (some cigarette lighters can pump out around 15V so be sure that the remote can handle this), you will have to continue using the existing battery.

Step 4:

The GSM Relay has 7 relays. The first is controlled by phone call. When called, the relay will open for a set amount of time that can be programmed into the device by text message. Mine is set for 1200 milliseconds.

I would recommend wiring the power cables into the device first. Take the 12V DC cigarette power cord and strip the ends of the cables and slide the cable through one of the ports on the side of the device. These ports can be tightened to ensure the device is weather proof. I fed the wire through the port closest to the power connector, but if your wires are higher gauge this can be difficult. Consider running the wire through the far port. The remote key fob will remain inside the device and its wires will not be run through on of the ports.

GND (ground) is clearly marked as the top most connector. Wrap the negative (black) wire from your remote key fob around the negative cigarette power connector wire and feed it into the GND connector. Screw it down tightly to ensure a solid connection.

Wrap the positive (red) wire from your remote key fob around the positive cigarette power connector wire and insert it into the +12V connector on the GSM device. Screw it down tightly and test both wires for looseness.

Step 5:

Next, run the wires from our “start” button into the relay controlled by phone calls. Each relay is simply a pair, with the first relay being controlled by phone call, and the rest being controlled by text message. Push the wires into each connector and screw them down tightly. Remember, the remote will reside within the GSM devices case, so do not run the wire through one of the case ports.

Once this is done, consider sliding a small plastic bag or ESD bag over the remote key fob to prevent any shorts.

Step 6:

Slide back the metal bracket covering the SIM chip holder to allow it to pop up. Insert the SIM chip as shown and press it down again, securing the metal bracket to hold it down.

The GSM device has 3 LED’s on it:

-One for network connectivity. This LED won’t turn on for the first 10 seconds, and then will blink quite fast when the device initializes. The rapid blinking means its searching for a network to connect to. Once it establishes a connection (this will only occur if the SIM chip is a valid one and the device is in GSM range), the light will blink much slower, indicating that the connection has been made.

-One for indicating power status (blinks regularly to indicate it is powered).

-One for indicating TX or RX. Whenever the device receives or sends a text message/phone call, this light will flash.

Connect the device to your vehicles cigarette lighter! The power LED should be flashing, as should the network LED. Once the device achieves network connectivity, the flashing of the network LED should slow down.

Step 7:

Programming the device is simple. I have attached a PDF to this Instructable containing the instructions. To quickly add a phone number to the list of valid phone numbers that can call the device (also called a white list), send the following text message to the device:


PWD is the password (which can be changed), and WHL01 is the first position in the white list. If you wanted to add a second number you would use WHL02, etc. and so forth.

The phone number to be entered should contain the area code and regular phone number with no dashes. Occasionally the international country code must be prepended to the start of the number, but try without this first.

Call the device and the first relay should loudly clack open and closed for 300 milliseconds (default length of time). The device will never pick up the phone call; rather it merely checks whether that phone number is in its white list, and then either ignores it or acknowledges it. It usually activates itself on the second ring and causes you to hear two rings to occur quickly one after another when it activates.

To update the length of time to one second, use this command:


Figure out how long you normally have to press the start button for to start your vehicle and then program the relay to open for the proper amount of time.

Step 8:

Time to test our device out. Call the device and watch as the TX/RX LED activates. The relay should loudly flip open, and if you have a small LED on your key fob like mine, you should see this glowing as the “start” button is pressed by our relay. If the timing is correct and the key fob is pressed, your vehicle should start!

The parts I used can be obtained from Rellay Supply. The direct link for the 7 switch device: GSM Remote Control Relay.

If you have any other ideas for projects let me know. I’d love to collaborate or try out new projects!

I found some really useful devices at Relay Supply but there are lots of other sites out there, and eBay has many items like this as well. Google is your friend! Find what works best for you.

Another type of device that can be useful are devices that don’t use bare contacts, but instead have mains plugs can also be found on Relay Supply. All units are Quad Band, and are either GSM based, or Wifi based, with multiple options for AC or DC power inputs.

Relay Supply – GSM Remote Control Relays. GSM AUTO, GSM CTL, GSM RELAY, GSM KEY available. Control any electrical device from your cell phone. Android and iPhone software included for free!
Relay Supply – How to start your car with your cell phone
Relay Supply – Instructables on how to start your car from your cell phone

GSM Relays, Switches, Gate Openers, and WIFI Relays from Relay Supply