Question for engine electronics wizards - VSS/Tach Signals

Discussion in 'Car Forum' started by Team Greenbaum, Nov 15, 2006.

  1. Team Greenbaum

    Team Greenbaum Millennium Member

    Likes Received:
    Jul 30, 1999
    After driving 2 mini-laps in the new Corvette at GM's "The Drive" in Las Vegas I decided that I had to have a heads-up display for my car (2006 Mustang GT). I bought a VSD Concept which looks great and has exactly the functions I need. Unfortunately, it's designed to be installed in import cars and the calibration is way off. I have the factory service DVD for my car so I can find any wire in the vehicle but I need help figuring out how to Mickey-Mouse the speed sensor and tach sensor connections so they work correctly.

    Speed Signal
    The instructions say "Connect to speed signal wire of engine computer unit." and "Applicable speed pulse: 2, 4, 8, 16, Free Pulse (1,051 pulse/mile~26,665 pulse/mile)". Based on my research, my car doesn't have a VSS (vehicle speed sensor) signal because everything, is controlled directly by the computer over the CAN (Controller Area Network). But it does have an OSS (output shaft speed sensor) and I thought that would be an acceptable alternative. I connected the unit to the OSS signal but the engine speed on the display is 5-10 times what my actual speed is, no matter which setting I make in the unit. Is there any way I can convert the OSS signal to a VSS signal? Is there any way I can tap into the CAN-BUS and extract a VSS from there?

    Tach Signal
    The instructions say "Connect to tacho signal wire of engine computer unit." and "Applicable Number of Cylinders: 3, 4, 5, 6, 8". Aftermarket tachometers are common for this car so I looked at instructions for those. That told me to connect to coil wire #1 and set the unit to 1 cylinder mode. After making all the connections I went to the unit's setup mode and realized that it didn’t have 1 cylinder mode. Is there a tach signal that encompasses all 8 cylinders? Would a tach adapter from Auto Meter or MSD do the trick?

    As with most of my other projects, this is turning out to be way more complicated than I first thought. :shocked: :shocked:
    Any and all help would be greatly appreciated!


    Likes Received:
    Feb 17, 2006
    the problem you are having with the speedo is designed that way so that you will "think" you are keeping up with a chevrolet! jk..
    most output speed sensors will use an ac voltage signal and the speedos will need to use a dc signal,in between the 2 is usually some type of buffer(converter).i would call the tech department of the speedo manufacturer,they can likely tell you what wire to pick up from..
    as far as the tach,that would have to come from the cks signal, i would have to look at a schematic,which i will try to do later.......