8

I am not an electrical or automobile engineer, so pardon my ignorance.

I found this product in the market to auto close power windows for certain brands.

How can we send signals to the CAN bus using an OBD interface? Does the automobile manufacturer expose such an API?

I have another related question.

Can we find out, using OBD, whether power windows/sunroof is open or not?

  • 1
    It all depends on the car and the manufacturer, you should read the Wikipedia page on OBD, it explains how it works pretty clearly – Keith M Jan 4 '16 at 1:11
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Everything depends on if the manufacturer multiplexed the windows or not.

For example, General Motors tends to multiplex their windows. This means that every door has a module inside it. The module controls the window, door lock, power mirror, etc... and takes inputs from door lock and window switches.

The only thing to pass through the door jam is power ground and network lines (mostly). When the driver pushes a button for the passenger window, the driver door module senses the switch input and sends a signal over the network to the passenger door module. The passenger door module then rolls down the window. With this kind of setup, a message can be generated on the network that will move a window. To be very clear, this is not an OBD standard function; it is specific to the manufacturer.

This interface is exposed on the network for diagnostics. I have personally rolled windows up and down with a scan tool. Unless the windows have position switches built in, then no.

If the windows are hardwired then it is not possible.

  • Thanks @vini_i . As you mentioned, rolling windows up and down using OBD is manufacturer/car specific. But what about just reading data related to whether power windows/sunroof are open or not? Even that is manufacturer/car specific? – rp1980 Jan 4 '16 at 2:18
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    @rp1980 yes, that's manufacturer specific too – Keith M Jan 4 '16 at 2:32
  • I like your answers better when they are formatted. You give a lot of data, when you do the bullets and stuff. Easier for a <human like me> to grasp the concepts. Great answer though. – Ppoggio Jan 5 '16 at 8:25

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