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Thread: LT1 to T56 VSS Issue

  1. #1
    Tuner MakesBadDecisions's Avatar
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    Oct 2017
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    Montucky
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    LT1 to T56 VSS Issue

    I have a Katech LT1 mated to a T56 running the E92 using a 2015 Denalli ECM and OS. The engine starts and idles after a 3 wire to 4 wire high side fuel pressure sensor and harness swap, no codes currently present.
    Issue I have is the VSS reads 158 all the time.

    Question i have is what ECM and OS will work with the T56 running a 2 wire vss? We currently have the 2 wire VSS into pins 6 and 7 in connection 2, per the Denalli wiring diagram. I have tried various input and field changes withing the ECM. The harness appears to be a butchered factory harness, with that said all sensors are working and reading.

    I assume that a OS change is needed along with possibly figuring out how to bring in a digital speed based on the camaro or vette wiring diagram.

    Any input would be helpful
    Thank You
    MBD
    2017 Crew Short 4x4 - 575hp/581trq at the tire
    2017 C7 GS 3LT - All stock for now, waiting impatiently for shop time to install parts

  2. #2
    Potential Tuner
    Join Date
    Apr 2021
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    1
    Did you ever figure this problem out? I have a similar (but different issue). I have a T56 connected to a Gen 5 LT1 from a manual transmission Corvette.

  3. #3
    Tuner MakesBadDecisions's Avatar
    Join Date
    Oct 2017
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    Montucky
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    We ended up using a Bowler t56 harness and used that VSS out into the ECM which gave us speedo, there was other issues going on with intermittent comms, random other electical issues and semi-unresponsive to tune changes. The final fix was to remove the customer provided cheap junk harness and replace with speartech harness and corvette OS. The tune lined out in a few revisions, speedo works and no more intermittent problems.

    I had already lost my ass enough on the job I never pin tested old harness and new harness to see what the potential issue in the wiring was.
    2017 Crew Short 4x4 - 575hp/581trq at the tire
    2017 C7 GS 3LT - All stock for now, waiting impatiently for shop time to install parts