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I am trying to implement remote control of a car, by connecting a GSM device to OBD port.

If someone is using my car, I need to remotely stop the vehicle by sending command. Upon sending STOP command, GSM receiver & control logic in car connected to OBD port should send command to engine ECU to cut-off fuel injection.

Is that possible?

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  • \$\begingroup\$ No, it isn't possible. A GPS receiver only receives GPS signals; you can't send commands through one. \$\endgroup\$
    – Dave Tweed
    Feb 14, 2015 at 14:43
  • \$\begingroup\$ Is the GPS device a tracker with OBDII functionallity? If so what device? \$\endgroup\$
    – RSM
    Feb 14, 2015 at 14:46
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    \$\begingroup\$ Sorry. It's GSM. Wrongly mentioned as GPS. \$\endgroup\$
    – Hegde
    Feb 14, 2015 at 15:29
  • \$\begingroup\$ @Hegde If it is GSM then the you need a micro like Gleison said. The other thing is if you made your OBD device or bought it, bought ones are blocked from sending over the CAN bus, while if you built it then it is possible if you have the ID for the injector and understand this might cause errors on the ECU, the best way would to install a relay or other device to interrupt the fuel line. \$\endgroup\$
    – RSM
    Feb 14, 2015 at 15:43
  • \$\begingroup\$ Thanks RSM. But if we open the relay in the fuel line, would it not cause other problems? like ecu will detect open circuit fault while diagnosing and turn MIL lamp ON? \$\endgroup\$
    – Hegde
    Feb 14, 2015 at 15:48

2 Answers 2

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OBD is a diagnostics output from your vehicle to give those who service it the state of the vehicle, diagnostic codes, reset options for errors and parts replacement initialization. This is as it only provides information from one of the layers of the CAN BUS.

You can maybe send commands through to the ECU for the Injector but this WILL cause you problems down the line. There are many sources for hacking your cars CAN lines, but this is restricted from everyday people for obvious reasons, as you might mess something up. The other thing is that you would need to know the specific PID and information for controlling the Injector.


THIS IS A WAY TO DO IT BUT THIS IS AT THE END USERS RISK AND MAY VOID WARRENTIES AND SUCH POLICIES


IMPORTANT

Please insure that if you ever activate the system it is moving at a safe speed, i.e. don't do it at 120 kph you would be better off activating it while the car is moving at less than 20 kph (or 12mph). This will reduce risk of accidents. The original employer insures this using GPS based speed before activation.


You can monitor the speed of the vehicle by monitoring the speed on the OBDII port, using the PID 0D, this is the speed in kph, found on wikipedia under Mode 1.

Below is the basic implementation of the method that is used to control the fuel pump power. It is not the entire control circuit as it is copyright by the employer.

schematic

simulate this circuit – Schematic created using CircuitLab

The NPN type can be a BC337.

  • The system functions in that when your GSM module gets the command, your MCU will activate the relay by making its GPIO high.

    This removes the ground from the pump starving the engine from fuel and thus not damaging the injectors(if its a diesel vehicle it will really damage them... lots of cost to fix).

    This way only starves the engine and thus stop it completely. This does work and is proven by tests and permanent applications in the field not to cause error messages.

This would be the safest way to do it as it will not cause your whole car to stop working by sending the incorrect commands on the BUS.

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  • \$\begingroup\$ Pleasure, hope it assists you. \$\endgroup\$
    – RSM
    Feb 15, 2015 at 6:08
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The cheapest way to achieve that is to use a GSM module. You could get a SMS with the module, and then a micro-controller would deactivate the car (supposing it would be possible through OBD).

There are solutions for tracking vehicles, bicycles, dogs, babies through GSM. I don't see how it should not work.

Edit: At sparkfun they have a GSM board for 60 dollars. It supports UART and SPI, it should pretty easy to hook it up to a MCU. https://www.sparkfun.com/products/9533

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  • \$\begingroup\$ But, is it possible to cut-off fuel through OBD port ? \$\endgroup\$
    – Hegde
    Feb 14, 2015 at 15:31

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