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Thread: E38 L96 with TH400 needs VSS?

  1. #1
    Potential Tuner
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    May 2016
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    E38 L96 with TH400 needs VSS?

    Hi there, ive been doing alot of research to figure out what to do in regard to getting a VSS signal into my 2011 savanna van E38 ECM. i am not at all a tuner, i am a guy who wants to learn! heres a little run down as to what i have just to give a little insight.

    -using HPT pro, version 3.0
    -2011 gmc savanna van L96 6.0 originally had a 6l90e behind it but not anymore
    -BTR stage 4 ls3 cam
    -th400 with 3000 stall
    -currently the tune is just what ive gathered off this site to get the car to idle with the cam
    -stripped the harness myself as per Lt1swap.com
    -it does not have a TCM incorporated in this harness
    - idles great without throwing codes, even drove it down the street so everything seems mechanically fine


    im worried as this car is going to get driven to the track and back around 30 miles round trip and at the moment im showing 158mph on the vcm scanner and do not currently have a VSS hooked up. im going to bring my car to the dyno very soon and think im going to have issues without a VSS while tuning the gen IV E38 ECM as it wont know if im either stopped or moving in gear.

    if i was to add a dakota digital sen-01-128 to my th400 will it fix the 158MPH issue? what is everyone doing with the truck/van E38's with a manual trans/th350/th400?

    my understanding is the ECM needs a sine wave and not a square wave and the dakota digital is a 3 wire sensor which makes me think its a hall effect but says its a sine wave but only has 1 output wire. would i just pin signal wire to the x1 pin 71 and set it to repTOS under SPEEDO>CALIBRATION>VEHICLE SPEED SENSOR?

    http://www.dakotadigital.com/index.c...rod/prd916.htm

    or is there a AC sine wave sensor that will work that has a hi/lo output to put to pins 71/72 on the x1 connector? that i can set my trans to manual under TRANS>ECM TRANS TYPE> MANUAL, that will work?

    if either of those ways or a way you guys suggest will register my E38 a VSS and fix my scanner from showing 158mph ill be extremly happy, ill do all the calculations to get it to work i just do not want any stalling issues while on coastdown, idle and drivabiltiy issues. i thank you guys tremendously as ive learned so much from all of you

    heres a post of my tune so far, its probably not worth post as per my question but here it is
    chevstang vats cleared idle tune startup.hpt
    Last edited by 81maliblue; 08-03-2016 at 09:32 PM.

  2. #2
    Tuner in Training
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    Sep 2012
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    I have a very similar setup. 2007 E38ecm originally for an LY6 / auto combination and I am now using a TH400. I got a pass-through Dakota digital VSS and hooked it to X1 71/72, but I still get 158mph. My tuner is using HPT and he said he set the transmission type to "manual", but it is still reading 158mph. I did some digging and found this thread: http://www.hptuners.com/forum/showth...4000-RPM/page4 It looks like there may be two different locations in HPT for changing transmission type and there is also a "speedo output" setting that may need to be disabled. Give that thread a read and let me know if you figure it out.

  3. #3
    Advanced Tuner Montecarlodrag's Avatar
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    You can't have a working speedo with only the E38 and automatic OS because the Vss is hooked to TCM, then the TCM sends the speed signal thru the CAN bus to the ECM.
    The only way to make it work without a TCM is to flash a manual OS to the ECM and hook the Vss to pins 71 and 72 of the X1 connector.
    There is no switch to change, you need to flash it with a Tech2 with a manual OS, HPT can't do it.
    9 sec Montecarlo SS

  4. #4
    Tuner in Training
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    I can't use a manual OS because the manual OS will not run the VVT. I am under the impression from that thread and cam's results that you can get the E38 to read VSS from X1 71/72 with an automatic OS.

  5. #5
    Advanced Tuner
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    Feb 2010
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    Its impossible to get the scanner to read properly, given the limitations of hpt. You can likely get your speedo working but the cruise wont work, and the scanner will never read properly unless you go to a manual OS. VVT was never made with a manual, you'll need to get a VVT delete kit. I have I raw hex fixed the scanner issue in the pcm, and got the speedo working but, cruise doesn't work in all gears.

  6. #6
    Tuner in Training
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    Oct 2014
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    I have a TH350 and had to set the variables to get the speedo close. I can probably get it spot on with some more testing but it's only off by 5mph right now. Like you said though, cruise control won't work. My car is a 96 Z28 w/Turbo 5.3