Curious if there are any projects out there in which someone controlled a remote vehicle starter with an Arduino board.

Specifially, I am considering a method to start my car at a preset time every morning.

I am thinking it would be easy to wire up an Arduino to the Remote Fob itself and send the signal to start at a set time (I am an Arduino noob and have not done anything but basic tutorials with a small Teensy board).

My specific system is two-way and sends back a success or fail signal after you attempt to start. It would be nice to program the system to try to start X number of times after a failure.

Has anything like this been done? Anything similar?


There seems to be some confusion...

My vehicle already has a Viper 2-way remote start system installed.

I would like to wire one of the existing key fob remotes to an Arduino board to control the remote itself (which sends the signal to start the car).

I do not wish to wire anything additional into the car, but basically just emulate the press of the remote button via the microcontroller.

Pics of the FOB PCB:

enter image description here

enter image description here

  • \$\begingroup\$ Not a real question. It will be closed. \$\endgroup\$ Commented Dec 13, 2011 at 12:41
  • 5
    \$\begingroup\$ @Leon: I see you saying "it will be closed" a lot, but you don't actually have the authority that implies. In a few cases the question wasn't closed. You can only say that you think it should be closed or that you expect it will be closed. \$\endgroup\$ Commented Dec 13, 2011 at 13:09
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    \$\begingroup\$ I agree this question is quite broad, but I'm waiting to see how things evolve before deciding whether it should be closed. \$\endgroup\$ Commented Dec 13, 2011 at 13:11
  • \$\begingroup\$ As far as detecting when the car is on...Some power plugs on the inside of some cars are only powered when the car is on (both my vehicles have these) - if that's case, anything plugged in there would only come on when the car is on. \$\endgroup\$
    – rfusca
    Commented Dec 13, 2011 at 18:16
  • \$\begingroup\$ "My vehicle already has a viper 2-way remote start system installed." Well then how about a picture of the remote fob out of its case! Basically you need to connect to the button switch and monitor an led for confirmation of a start, right? \$\endgroup\$
    – SteveR
    Commented Dec 13, 2011 at 18:40

2 Answers 2


All of the Remote Starter systems I have seen are aftermarket products. In fact, most auto dealers use these after market products when installing them in new vehicles. It should be easy enough to find the manufacture of yours, and send for a replacement remote fob. Once the fob is programmed to your vehicle, you can hack the contacts to your new circuit.

As far as sensing the engine running most of these units use a sample of the engine RPM (tach) and detect the pulses. The RPM outputs on the ECU of the vehicle, and is probably already tapped to use for the Remote Start unit. For the report back function, you can buy a remote fob & receiver and hack it in much the same way as your starter key fob.

EDIT: After reviewing the new information and pictures, I will revise my answer to the following:

If the led in fig 1 (lower right corner) is the confirmation of a start indicator, then a photo transistor can be optically coupled to this led through something like a short hose or tube. This can then be an input of the Arduino.

EDIT 2: In fig 1, middle of the board may be a tactile button switch to initiate a start. If this is the case, a relay could be connected to the Arduino output and wired to the tactile switch in parallel.

  • \$\begingroup\$ How does the a car's +12 rail after it starts compare with the voltage before? I would think that after a car starts, the rail would be both higher and noisier than immediately before. \$\endgroup\$
    – supercat
    Commented Dec 13, 2011 at 17:43
  • \$\begingroup\$ @Supercat - The cars voltage will increase when the car starts. Should be between 13-14VDC, typically 13.8V. So yes the increase in voltage can also be used to detect a successful start. This method is also used in remote starters. The RPM detected method is usually preferred as it detects an engine start sooner therefore disengaging the starter motor sooner. However either method will work for this project. \$\endgroup\$
    – SteveR
    Commented Dec 13, 2011 at 18:23

This is a very broad question, so can only be answered in generalities.

You might possibly find a description of the protocol between the fob and the car, but not the passwords used with your particular car. Usually these include rolling codes with only the hashed results sent over the air. Therefore listening in on a few transmissions won't tell you what the code needs to be for the next transmissions. In practise, it will be simpler make the existing key fob do the transmissions. Maybe you can rig up something so that the arduino activates a solenoid which pushes a button on the key fob.

As for determining success, that's all up to you. Maybe you can put a sensor by your car that detects it is running. Something under or near the car looking for steady noise might work, or maybe detecting the spark if it's a gasoline engine. Maybe some sort of IR sensor looking for exhaust heat. These are just ideas. I've never actually done a car-running detector.

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    \$\begingroup\$ I gained the impression (possibly wrongly) that he intended to wire across the fob button so just a key closure was needed. For the car running detector brain mediated audio feeback usually works a treat :-). \$\endgroup\$
    – Russell McMahon
    Commented Dec 13, 2011 at 13:20
  • \$\begingroup\$ @Russell: Yes, he did mention wiring accross the button. However, I think it would be good not to hack the fob unless you really can't come up with another reasonable way. That part of the fob is likely factory sealed for good reason. A lot of engineering to deal with environmental conditions went into the fob, whether apparent or not. I would want to leave all that intact if I could. \$\endgroup\$ Commented Dec 13, 2011 at 13:30
  • \$\begingroup\$ Yes, I would like to wire into the FOB..I have two so I am willing to sacrifice one. The hacked fob would remain in the house wired to the controller permanently. \$\endgroup\$
    – stephen776
    Commented Dec 13, 2011 at 18:54

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