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Mode 22 help?

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  • Mode 22 help?

    I am new to this forum and writing my own ELM based digital dash. I have things setup to individually read values from the ECU (mode 1), but would like to extend to features I suspect are in Mode 22. I have an ECU from a 2000 vette in a vehicle I can test with, and another from a 2002 GM on the bench. What I am looking for is the standard stuff to flow near real-time if possible from the ECU (RPM, Speed) and the other stuff (Water Temp, Oil Press, Volts) could actually be polled. Is there a way to have the ECU just send me these values? I've seen a couple of posts that indicate that is possible provided you send keep alive packets every once in a while.

    Any pointers to documentation on this would be greatly appreciated. This is just a hobby for me, planning on putting a digital dash in my '65 GTO that I am currently restoring.

    Thanks in advance for any help/pointers.

  • #2
    What is the problem with requesting the data that you need, as opposed to coercing the ECU to periodically push this data to you?
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    • #3
      No real problem asking for the data each time, just thought there might be a more efficient way to do this. The RPM and Speed are the ones that i was hoping I could just tell the ECU I wanted on a stream basis.

      Is this the way most of the scanner products work, send each command and display the results? I was just thinking that this was a lot of two-way data on the serial bus. But, if that is the way it's generally done, makes what I want to do fairly straightforward.


      • #4
        With GM.. most of the mode $01 pids translate into mode $22 pids.. So if you want PID $0C, you can use mode $22 PID $000C.. (just add a preceding $00).

        The rest of the PIDs are enhanced stuff and proprietary. You can purchase them through a trade organization called ETI ( But it is very expensive.. and those who get the data are not allowed to share it.. (of course).

        Good luck.
        Hack your car's CAN BUS at