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Tach Issues with b18c1 swap (which wire?)

Discussion in 'HYBRID -> EG-EK / DC' started by BlackBoosted2, Mar 16, 2004.

  1. BlackBoosted2

    BlackBoosted2 Junior Member

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    I just put in the proper p72 obd1 ecu and my tach doesnt work.

    We are unsure why since this is not a common thing to happen with swaps. The engine runs fine, and runs quite well I might add...but no tach.

    We can rewire it, but does anyone have any suggestions? I have looked at wiring around the net after searching, but nothing we can find is related to a tach issue.

    The car is a 94 Si hatch, and the engine is an obd2 w/obd1 p72. obd2 engine harness, obd2 distributor . . .

    No codes are thrown, I just have no tach!

    There is an extra plug that was not used from the obd2 engine harness, it contains 3 wires and is located next to the passenger side harness plugs into the firewall..

    I know the middle wire is for the Knock Sensor, and what are the other 2?


    Searching has not helped..
     
  2. BlackBoosted2

    BlackBoosted2 Junior Member

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    Searching hasnt helped me

    Anyone have any ideas? I want to keep the stock cluster
     
  3. JDMilan

    JDMilan Senior Member

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    not sure why, i even ran the GSR p72 along with a b16 for a while, with codes...


    and my oem tach still worked,,,probably a wiring issue. make sure all cluster associated connections are tight and working, check for voltage.
     
  4. nonvtec

    nonvtec Junior Member

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    I'm having a similar problem, 2000 obd2b gsr motor and wiring harness and obd1 car and no tach, runs with no check engine light, jsut no tach so far
     
  5. pissedoffsol

    pissedoffsol RETIRED

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    the tach is the blue wire off the distributor.

    chances are you wired the distributor wrong, or even more.

    why would you use the obd2 harness is beyond me.

    the easiest way to wire up a swap liek yours is to use the oem Si harness.
    swap the plugs for the distributor, injectors, and altenator- simple cut and paste. for the distributor, there are 2 plugs on obd1, and 1 on obd2. the wires transpose by place. you'll know what i'm tlaking aout when you look at it.

    then, you need to run the iab control wire and the knock sensor if you're running the p72 ecu.

    if you do that, you will have no codes and the motor will be wired up 100% correct.
     
  6. rcoolb2002

    rcoolb2002 Member

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    No .. the easiest way to "wire up a swap liek yours" is to leave the existing wiring harness on the motor and plug it in. Everything plugs right up you just have that extra plug on the passenger shock tower side. Everything will run fine. Since i dont have a tach in my gauge cluster... i dont know whether that extra plug is the issue or not. I just use an aftermarket run to the disty.

    *edit* this is assuming you are running a chipped obd1 ecu to ignore the knock sensor etc.
     
  7. nonvtec

    nonvtec Junior Member

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    Well the way i did it seems to be working jsut fine, the tach was not working because on obd2b they ran the tach off of a seprate signal to fro mthe ecu and there was not a wire ran from the blue wire on the dizzy to the tach, just the one ran to the tach. and the vtec wires seem to be right too, no check engine lights and runs smooth, thanks for the help
     
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