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ECU & Tach Signal

Discussion in 'ECU's, Electronics, and Tuning' started by reckedracing, Jul 6, 2006.

  1. reckedracing

    reckedracing TTIWWOP VIP

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    Does anyone know if the ECU receives a tach signal?
    The manual Says the tach signal is something like 100 rpm for every 250 pulses from the igniter, but I would think the ECU receives a signal too.
    What pinout is the signal?

    I am also wondering what pinout on a P28 is the O2 signal?
     
  2. reckedracing

    reckedracing TTIWWOP VIP

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    PO2HA06Orange/black i think this is Primary 02
     
  3. reckedracing

    reckedracing TTIWWOP VIP

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    ICMA21Red/Green




    would this provide a good tach signal?
     
  4. pissedoffsol

    pissedoffsol RETIRED

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    blue wire off the tach on obd1. not sure for obd0

    pinouts are in the reference scetion.... but you knew that, right?
     
  5. reckedracing

    reckedracing TTIWWOP VIP

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    yea, i pulled the pinouts from above from the refrence section...
    i'm confident on the O2 singal...
    but i'm still thinking the "tach signal" doesn't enter the ECU at any time...
    i think the ecu sends the ICM (ignition control?) signal, but that does not correspond correctly to the rpm's
    am i wrong? should i just run a tach straight to the blue wire in the engine bay?
     
  6. pissedoffsol

    pissedoffsol RETIRED

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    tach singal does enter the ecu - has to. how else will it know when to rev limit? :p not sure on what wire brings it though. but the blue wire goes to the cluster. tap off that for your tach lead.
     
  7. reckedracing

    reckedracing TTIWWOP VIP

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    ah yea, that does make sense...
    i figured it had to for the vtec switch-over, never thought of the rev limit, but i'm thinking the ECU gets the ICM signal which does not correctly correlate to RPM...
    i dunno, nevermind
    lol

    thanks for the help B
     
  8. Sofa King Slow

    Sofa King Slow Member

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    I can't add the image, but the engine speed output signal (RPMs) does not enter the ECU at all. It leaves the Ignition Control Module in the distributor via a solid blue wire and from the splice goes to the tachometer, the cruise control box (if installed), and the tach test connector (white 2-pin connector) on the driver strut tower.
     
  9. 99sidude

    99sidude Moderator Moderator VIP

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    I have an obd1 civic dx. For my tach install, I had to tap into the blue wire on the engine harness. The wire is located on the drivers side shocktower set of plugs.
     
  10. Sofa King Slow

    Sofa King Slow Member

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    I need to clarify myself before I am corrected. The RPM signal from the dist does not enter the ECU. I would imagine the ECU gets RPM input from the CKP or creates its own using output to the injectors.
     
  11. reckedracing

    reckedracing TTIWWOP VIP

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    i think the ecu uses the ICM to determine rpm
     
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