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Thread: VSS doesn't work at low speeds between 0-5MPH

  1. #1
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    Oct 2017
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    VSS doesn't work at low speeds between 0-5MPH

    I'll start off by describing my build "Project Wundrer".

    I have a 1989 Jeep Cherokee that I've swapped in a 5.3L LMF from a 2009 Chevrolet Express Van. Its has a 231c transfer case with a http://www.jbconversions.com/product..._short_sye.php kit for the output. It has a 40 tooth tone wheel and I've replaced the sensor once already with a OEM replacement.

    Everything is working how I want it to but when I take off from a stop the VSS won't register till its over 5 MPH. I've attached two files.

    The VCM Scanner file shows what the VSS is doing.

    In the tune I set up the correct gear and tire size. I've disabled 'Wheel Speed Sensor' under the hardware and then changed the 'Speed Out Put' type from Wheelspd to Vehserial. Should I revert this back? I've couldn't tell the difference between the two settings.


    Thanks in advance!!!!
    Attached Files Attached Files
    Last edited by FunkyParts; 12-11-2017 at 08:59 PM.

  2. #2
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    I finally was able to hook up an oscilloscope to verify the signal. The Variable Reluctance (VR) sensor that GM uses signal strength is affected by how far and fast the tone wheel spins. I ended up removing about 3mm of the mating surface from the sensor to bring the sensor closer to the tone wheel. This provided a stronger signal at lower speeds.

  3. #3
    Senior Tuner 10_SS's Avatar
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    Mar 2012
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    Detroit, MI
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    The stock setup is really bad as well, 2010 Camaro SS manual for example. Takes a few MPH, few seconds for it to start showing up as well. Tried to overlay it on a video at the track, it was really bad.

    I compare Driven wheel to Undriven wheel speed, and the difference is insane. Looks like Driven wheel speed is the tail of the trans, and undriven is the ABS system for fronts. I use it to log wheelspin which I get a lot of. I guess driveshaft speed isn't that important since it uses wheel speed for ABS/Stability. Problem is, I dont think there's a way to get the ABS readings for the rear wheels. Maybe HPT could find it.
    2010 Camaro LS3 (E38 ECU - Spark only). MS3X running complete RTT fuel control (wideband).
    Whipple 2.9L, 3.875" Pulley, kit injectors, supplied MSD Boost-A-Pump, stock pump
    LG Motorsports 1 7/8" Headers - No Cats, stock mid pipe with JBA Axle Back
    ZL1 Wheels/Tires

  4. #4
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    Any chance you have your Camaros base tune handy?

    I'm trying to convert from a mechanical to electric radiator fan. I read in another post that 2010 Camaros have the correct setting to run electric.