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Thread: CAN Bus Messaging to Control Engine on Dyno

  1. #1
    NPD is offline
    Join Date
    Sep 2015

    CAN Bus Messaging to Control Engine on Dyno

    Good evening,

    My name is Tom and I live in MN. A kind individual directed me to this website from the HP Tuners Forum. I am wondering if someone could help me out. Does anyone have experience sending and receiving CAN messages on the CAN bus for the GM Gen IV ECMs, like the E38 for a 4.8L? In particular, I am looking for a person or resource on how to send hexadecimal instructions to the ECM to make the engine react, like increase the torque request from idle to full throttle during a dyno run. I have a CAN Bus analyzer by Microchip and viewed the GM Tech 2 throttle up requests. However, sending this message on ID 0x7E0 for diagnostics will only get the engine to increase to 2050 rpm. I can only apply small amounts of torque as well in this mode.

    I was thinking about sending an instruction for cruise control acceleration but am unsure how to construct the message to send. To boot, I only have the ECM, harness and engine to work with and no access to a vehicle is goes in. This is all dyno testing.

    Any help would be greatly appreciated.

    Thank you!

  2. #2
    Maximum Bitrate
    Join Date
    May 2012
    Grandville, MI
    I hate to say it but you are seeking the holy grail...

    This information is not publicly available from GM and is generally found by trial and error.
    You have two different routes you can go with this...

    Find someone that already has this information (And if you find someone I certainly would like to know those codes too) or you have to have a similar vehicle to reverse engineer.

    If you are a business developing software for the industry you CAN purchase the information from GM but you are talking like $7000 for 1 year of access to the information and signing a NDA. So the information is not easy to come by.

    In most cases I have experienced that GM tends to keep things in the same generation the same across the board for simpler control. In other words, if you find the information you are looking for in a 2002 Cavalier it is likely the same code for a 2015 Silverado. Not 100% but in most cases I have seen... has some forums that have more active people trying to do things via ODBII or canbus.


  3. #3
    FLAC rray's Avatar
    Join Date
    Apr 2012
    SF Bay Area
    I have not sorted through the whole thing, but there is the GMLan Bible, which is a Google Docs sheet that has lots of the hex codes. Don't even know if it includes what you need, but it might help you map out what you need. The tabs are at the bottom of the page for each sheet.

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