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Thread: Ecu reset procedure.....

  1. #1
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    Default Ecu reset procedure.....

    With my gearbox woes and whatnot, while I had the firewall covers off, and prompted by another thread, I took my ECU out and resoldered/reflowed the solder joints between the PCB and the connector terminals.

    Now I've warmed the car up and am trying the 'restart the the car and not touching anything and let ECU self learn it's basic settings'..... For quite probably the first time the car is actually changing revs and seems to be doing something....

    My question is how long is this supposed to take before I decide it's actually an unstable idle bouncing between 900 and 1500 rpm randomly? Does it give you a clue as to when it might be mostly happy??


    Ooo idle getting down to 800ish on occasion now.. then back to 1200.... And down, and up......
    Last edited by britlude; 20-04-2019 at 01:19 PM.
    aka Jonathan!!

    '92 charlotte green auto.... as a daily
    '37 Ford Y street rod......... something for the weekend!

  2. #2
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    Presumed that your base idle air control is within the targeted spec (must be adjusted with fully warmed up engine but load condition depends on the non-DBW/DBW).

    Presumed no CEL, misfire, seized a/c compressor, etc.


    During the re-lean process, the only time the rpm stays at higher region is the first 5sec-ish immediately after starting the engine.
    Thereafter, rpm would be forced to stay at the specified idle rpm controlled by ECU through EACV (non-DBW) or stepping motor at the TH body (DBW).

    If rpm goes up and down during the process, you have a certain issue and the ECU won't re-learn properly.

    ECU reset must be done with fully warmed up engine under no load condition.


    From what you wrote, you already knew the followings but in case someone searches;

    1. Go out for short driving session to fully warm up the engine or just start the engine and wait until the rad fan kicks in.

    2. Once fully warmed up, make sure no electronics devices such as A/C CCU, power window, head lights, audio head unit, etc are in use and then stop the engine.
    Depending on the spec of aftermarket parts or modifications on your NSX such as DRL, ICE, etc, you may need disabling them.

    3. Pull out 7.5A CLOCK fuse and wait for 10sec.
    Put the fuse back in place.

    4. Start the engine immediately without touching the TH pedal or any of the electronics devices such as the ones mentioned above.

    5. The rpm would hung at around 1,200 - 1,500rpm for about 3 - 5sec immediately after starting the engine but would drop to about 1,000rpm and then down to the specified targeted idle rpm (MT/AT dependant) within the next few seconds.

    6. Keep running the engine at idle rpm without touching the TH pedal or any electronics devices for the next 10 - 15min.
    The rpm will change slightly when rad fan kicks in but that's normal.

    7. Stop the engine and re-start.
    This time, the rpm should drop to targeted idle rpm within a few seconds.


    For the clarification, the ECU can re-learn the long term co-efficient factors without going through the above procedure through multiple driving cycles.
    It's just quicker by carrying out the above process.

    As a side note, above process is carried out with fully warmed up engine that your CAT, O2 feedback, secondary air, etc flags (depending on the spec of your NSX) won't be set until you re-start the engine after cooled down and go through the driving cycle(s).
    Depending on the country spec, you will need multiple drive cycles to set all flags but for JDM and European spec, normally one drive cycle after cooling down the engine will set all of the flags on our NSX.


    Kaz
    Last edited by Kaz-kzukNA1; 20-04-2019 at 02:29 PM. Reason: extra info regarding rad fan

  3. #3
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    Thanks for that info Kaz, not sure I've seen the complete procedure written in one place before!!

    I have no CEL codes, everything as it should be, just the idle high/unstable and the intermittent gearbox losing its TPS signal (code 3) error. Is the sensor 5v reference generated in the ECU? I've seen it on a diagram as ''control unit' but it seemed vague! I have new air control valves to go on when I get a chance to fit them!
    aka Jonathan!!

    '92 charlotte green auto.... as a daily
    '37 Ford Y street rod......... something for the weekend!

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    Just when you think it's calmed down it wanders off again....
    aka Jonathan!!

    '92 charlotte green auto.... as a daily
    '37 Ford Y street rod......... something for the weekend!

  5. #5
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    Quote Originally Posted by britlude View Post
    ...and the intermittent gearbox losing its TPS signal (code 3) error.
    Sounds fishy. I'm not aware of the full story but is the 12V battery good and all ground cables perfect? I've once had a car (of my friend) who lost connection to ... due to a battery being too small for the car. The voltage dropped and the connection between electronic modules went south and it's thrown a code 'lost connection'. Just a basic input.

  6. #6
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    battery is fine, doesn't seem to be any power issue, but i shall check earths...

    ... another thing, it does seem to be running rich too....
    aka Jonathan!!

    '92 charlotte green auto.... as a daily
    '37 Ford Y street rod......... something for the weekend!

  7. #7
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    Having watched your erratic idle video a couple of times is it possible youíve missed a slight air leak somewhere, Iím sure if anyone on this forum would diligently check all possibilities then it would be you but from what Iíve seen and read there are many places the air leak could come from, O rings, gaskets, joints or even slight hair line fractures.

    What a nightmare symptom you have. 😰
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  8. #8
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    If you think it's an air leak somewhere you could use a fog/smoke engine in the intake and pull and twist on all hoses. What about the injectors and injector seals?

  9. #9
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    Watched your video. That's not even staying within the idle control region, lol.
    ECU will re-learn something but don't know what will happen within the idle control window.

    Similar to another factor causing EACV to hit its max/min limit and ECU just compensating it back and forth or you have other issues.

    The TH butterfly should be at constant closed position for non-DBW spec.

    AT selector signal sent to the ECU has to be constant during the process.

    Fuel pressure should be fairly steady even with your rpm behaviour.

    You could disconnect both F & R O2 sensor connectors to force the ECU into open loop.
    This may or may not prove anything if the engine getting extra air intermittently such as cracked vacuum tube changing the amount of external air with engine vibration.

    Just a matter of interest, where about does the base idle air adjust screw at the TH body sit from fully closed position?
    I won't touch it as you may have other issues and adjusting it without fixing other issues first will introduce new issue/factor later.
    But, with thoroughly cleaned TH body, for both the non-DBW and DBW model, somewhere around 3/4 opened from fully closed position is a good example.
    That's how the TH body left the factory.

    Probably you have already seen other examples but this is what you would see during the reset sequence on non-DBW model.
    DBW one would behave slightly differently at the beginning but as mentioned below, once it reaches the target idle rpm, it will be the same.
    Please ignore the temperature gauge as my sender unit has problem (incorrect resistance and slow response) for ages.
    Just waiting for the next coolant service.

    It's boring once it reaches the targeted idle rpm (depends on the MT or AT) so I just shortened the video as the rpm just sits at the target for the rest of the process.
    Couldn't position my gymbal through the steering wheel so apology for the shaky video.



    Kaz
    Last edited by Kaz-kzukNA1; 23-04-2019 at 04:08 PM. Reason: extra info

  10. #10
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    OT and just curious: what is the red symbol in the lower center of the instrument panel. I haven't seen this before.

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