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Thread: tapping tachometer wire?

  1. #1
    Constant Bitrate DrStein99's Avatar
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    tapping tachometer wire?

    Does anyone know where to find the wire assignments for the harness in the dash-board / steering column? I know there has to be a website, or chart somewhere, I dont have any luck finding it.

    I have a 1995 Nissan Maxima, trying to find the tachometer lead - it should be a wire that delivers a +12v pulse, each engine rev.

    I'm trying to build some neat gadgets using pic/eProm software, that gathers info from the car; and I want to capture the RPM's - if possible.

    Please advise.
    www.RAIDGEAR.net Engineering :: Research, Development and Art - all is one www.DrStein99.com

  2. #2
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    Tachometer- white/green (ECM)


    NISSAN, MAXIMA, 1995, Tachometer

    The ECM is located in the front of the center console on the transmission hump. The wiring is easily reached by removing the small black panel just to the front of the center console on the passenger side. the wire is in the middle row, 7th one in from the left.

  3. #3
    Newbie Mercury_Vapors's Avatar
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    I dont know if you'll get much out of it.. the tach wire is just a wire that sends pulses of DC current to the injectors.. i'm not sure if it changes when it goes through the firewall and connects to the ecm.. just my 2 cents.

  4. #4
    Constant Bitrate old_lou's Avatar
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    why not try making your own tacho pick-up, need a sender on the engine and receiver to count the pulse.
    http://www.niksula.cs.hut.fi/~mdobru...cho/tacho.html
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    Maximum Bitrate fixerofallthing's Avatar
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    Here you go. Let me know if you need any other help.Name:  diagram.jpg
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  6. #6
    Raw Wave shotgunefx's Avatar
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    Quote Originally Posted by DrStein99
    Does anyone know where to find the wire assignments for the harness in the dash-board / steering column? I know there has to be a website, or chart somewhere, I dont have any luck finding it.

    I have a 1995 Nissan Maxima, trying to find the tachometer lead - it should be a wire that delivers a +12v pulse, each engine rev.

    I'm trying to build some neat gadgets using pic/eProm software, that gathers info from the car; and I want to capture the RPM's - if possible.

    Please advise.
    I'm doing something similar for my own front end. I'm going to tap off the rpm/tach and indicators, read them with a PIC16877a and send them serially to the pc.

    If at all possible, try and hit ebay for the service manuals for your car. I've found them to be invaluable.

  7. #7
    Raw Wave shotgunefx's Avatar
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    Quote Originally Posted by fixerofallthing
    Negative (-) side of the ignition coil.
    I think you'll have problems with reading it from there with a PIC or other mcu. It's very noisy, electrically.

  8. #8
    Constant Bitrate DrStein99's Avatar
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    Quote Originally Posted by snova031
    Tachometer- white/green (ECM)


    NISSAN, MAXIMA, 1995, Tachometer

    The ECM is located in the front of the center console on the transmission hump. The wiring is easily reached by removing the small black panel just to the front of the center console on the passenger side. the wire is in the middle row, 7th one in from the left.
    --------
    There are about 3 black panels, all the center of my maxima, and I dont recall any on the passenger side.

    Am I looking in the hump (floor) or the one facing forward - the dashboard?
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  9. #9
    Maximum Bitrate fixerofallthing's Avatar
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    Quote Originally Posted by shotgunefx
    I think you'll have problems with reading it from there with a PIC or other mcu. It's very noisy, electrically.
    You are right. That particular car is coil on plug though, so there are 6 coils. So my first response was incorrect. I posted a pic of the wiring diagram for that vehicle and the wire mentioned above is correct. It will be a very "clean" signal because it is produced by a control module for the express purpose of running the tachometer.
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  10. #10
    Maximum Bitrate fixerofallthing's Avatar
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    Name:  untitled.jpg
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    The Car 2005 Scion xB

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