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Thread: 2021's that can't be flashed via OBD2 port

  1. #1
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    2021's that can't be flashed via OBD2 port

    So is this an issue with all the 2021 GM vehicles or what? I'd dealing with a truck but wonder if the cars are like this too. You can scan via the OBD port but can't write to the ECU. I had to make a ECU wiring harness to plug directly into the ECU to write to it. This is driving me nuts. Takes me 10-15min every time I reflash this vehicle. Is everyone having this issue on all 2021's?

  2. #2
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    Global B or VIP architecture have most or all modules isolated by the serial data gateway module.

    All CAN messages go through the SDGM to make sure they have the correct security protocol.

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    If I was you splice into the CAN wires in the harness right by the ECU and just have a second OBD port, could that be a work around?

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    Quote Originally Posted by C5turbo View Post
    So is this an issue with all the 2021 GM vehicles or what? I'd dealing with a truck but wonder if the cars are like this too. You can scan via the OBD port but can't write to the ECU. I had to make a ECU wiring harness to plug directly into the ECU to write to it. This is driving me nuts. Takes me 10-15min every time I reflash this vehicle. Is everyone having this issue on all 2021's?
    What kind of vehicle is it? I know that some of the supported GM vehicles run into trouble with the serial gateway module blocking any comms from tools trying to do non OE things.

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    Quote Originally Posted by cadillactech View Post
    Global B or VIP architecture have most or all modules isolated by the serial data gateway module.

    All CAN messages go through the SDGM to make sure they have the correct security protocol.

    hpt doesn't support any Global B applications yet. However, some Global A vehicles also use a wholly isolated gateway module. The 2021 Colorados have that as do some other vehicles.

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    Yep, it's a Colorado/Canyon truck.

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    Quote Originally Posted by tunerpro View Post
    hpt doesn't support any Global B applications yet. However, some Global A vehicles also use a wholly isolated gateway module. The 2021 Colorados have that as do some other vehicles.
    Ya, I meant to say many other Global A vehicles the SDGM as well. OE's are all over CAN bus security now.

  8. #8
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    Quote Originally Posted by C5turbo View Post
    Yep, it's a Colorado/Canyon truck.
    You might be able to wire in a dedicated DLC for the ECM/TCM but it may mess with the CAN bus as you would still be tapped in to the other modules on that isolated bus.

    If you do try, let us know if it works!

  9. #9
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    Quote Originally Posted by C5turbo View Post
    Yep, it's a Colorado/Canyon truck.
    GM added a security module(similar do 2018+ dodge) that needs to be bypassed in order to read/flash. Currently the only way is to read/flash via bench harness in those applications.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"