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Thread: Error With CVT Transmission module control

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    Error With CVT Transmission module control

    Hi everybody,

    In original my car without Ds mode function with the part number: 8631B405, so I buy the ECM CVT with part number 8631B404 from the UK market. When I replace CVT ECU 8631B404 in my car, I got the problem following:
    1. The instrument cluster to display transmission range switch N, D, L R not stable, flashing continuous like the video in below.
    https://www.youtube.com/watch?v=BVqzf4uWg5E

    2. When change the shift lever assembly from the P to R or P to D, the shift gearbox of the car is jerky, it doesn't like normal.
    3. When I connect with the PC through OBD port using the VCI cable & MMcodingwriter to read DTCs, some error appear like the picture as below.
    https://imgur.com/a/0zVRVJ6

    Everyone who know this situation can help me to solved or give me some advise. Thank you very much!



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    What is the original problem before you replace the TCM? do you have the DTC?

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    The problem also have with replacement new ecu. When I put back, use the original ECU without any abnormal

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    are you doing all this just to add Ds to the car?

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    Hi mohammad,
    Yes, i would like to add the Ds function in my car, in my country CVT ECU (8631B405) without Ds functional, that why I buy the old one (8631B404) from UK market. And when I replacement, it happrn. Do you have any idea?

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    Quote Originally Posted by pandafool171 View Post
    Hi mohammad,
    Yes, i would like to add the Ds function in my car, in my country CVT ECU (8631B405) without Ds functional, that why I buy the old one (8631B404) from UK market. And when I replacement, it happrn. Do you have any idea?
    is the part no of the cvt with Ds and without Ds the same?if not it wont work, but if some reason that they are the same you also need to replace the inhibitor switch.

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    Quote Originally Posted by allrock View Post
    is the part no of the cvt with Ds and without Ds the same?if not it wont work, but if some reason that they are the same you also need to replace the inhibitor switch.
    I am not sure about this, I think that is the same, but now it not working like normal, so maybe you right. Do you have any idea about the inhibitor switch, I don't understand what you say about this, could you please make it clearly for me?

    I also read the DTC from my car, the CVT/AT/TC-SST - 8631B404 error:
    - P071C
    - U0121
    - P071B
    - P0977

    Also attached picture as comment above.

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    Quote Originally Posted by pandafool171 View Post
    I am not sure about this, I think that is the same, but now it not working like normal, so maybe you right. Do you have any idea about the inhibitor switch, I don't understand what you say about this, could you please make it clearly for me?

    I also read the DTC from my car, the CVT/AT/TC-SST - 8631B404 error:
    - P071C
    - U0121
    - P071B
    - P0977

    Also attached picture as comment above.
    Quote Originally Posted by pandafool171 View Post
    I am not sure about this, I think that is the same, but now it not working like normal, so maybe you right. Do you have any idea about the inhibitor switch, I don't understand what you say about this, could you please make it clearly for me?

    I also read the DTC from my car, the CVT/AT/TC-SST - 8631B404 error:
    - P071C
    - U0121
    - P071B
    - P0977

    Also attached picture as comment above.

    - P071C malfunction Ds position switch(stuck off)
    - P071B malfunction Ds position switch(stuck on)
    - P0977 malfunction of high clutch and reverse solenoid valve (open circuit/short to power supply)
    - U0121 CAN timeout error (ASC)


    i dont think this will work based on your DTC on P071B and 71C the ecu determines that your switch is stuck which means you have the wrong switch lever while the P0977 the CVT cannot engage the high clutch and reverse solenoid because the command from the ECU is wrong that is why the system considers your ECU as open circuit because the command the CVT received is wrong.

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    Quote Originally Posted by allrock View Post
    - P071C malfunction Ds position switch(stuck off)
    - P071B malfunction Ds position switch(stuck on)
    - P0977 malfunction of high clutch and reverse solenoid valve (open circuit/short to power supply)
    - U0121 CAN timeout error (ASC)


    i dont think this will work based on your DTC on P071B and 71C the ecu determines that your switch is stuck which means you have the wrong switch lever while the P0977 the CVT cannot engage the high clutch and reverse solenoid because the command from the ECU is wrong that is why the system considers your ECU as open circuit because the command the CVT received is wrong.
    Hi allrock,

    I am not sure about this. I have checked the wiring connection also from the lever shifter to CVT ECU, I follow the original designed, not change any wiring to the ECU. Moreover, the cluster instrument also display the correct inhibitor (P,R,N,D,L) when I move the lever shifter (although R,N,D,L flashing On/off as the same video I post in youtube as link above, and Ds mode function random successfully). So I think the problem not come from there. Beside of this, I can not find any information or resource document, datasheet, etc... of CVT 8631B405 ECU or CVT 8631B404 ECU for check the pin in/out of the ECU.
    If you think the wrong wiring connection from the inhibitor switch on lever shifter to the ECU. How I can checked with this? please give me some advise. thanks for it

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    I've read the other thread the problem is all the available manual doesn't have that Ds on the inhibitor switch my manual also doesn't have you need to find a manual with the Ds mode so that you can determine where that signal is going..did you happen to compare the pin outs between the 405 and 404 ecu? and also you need to determine the difference on the inhibitor with the one with Ds and without..Name:  Screenshot 2021-11-26 161620.jpg
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