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Thread: ALRIGHT ,ALRIGHT ,ALRIGHT#2

  1. #1
    Electronic Ignition!
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    ALRIGHT ,ALRIGHT ,ALRIGHT#2

    Oops! i think its well past time that i should be moving out of the "introduction" and over here. this is from my yesterdays post

    To have readings from the PCM for the 94 B carline the DLC has to include M ( the serial data D29) from the PCM as well as B (D20 output field service enable) and A ( the ground)? I talked to Bob @ OBD1 Diagnostics and asked a few questions and he mentioned that no data would flow unless "M" was connected. It is not! Way back when, i was told i only needed B and A , i did tag the D29 wire coming out of the PCM along with a few other wires for reference noting. So i'll hook D29 up to the DLC in the next day or so and see how that works.

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  3. #3
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    Quote Originally Posted by steveo View Post
    you need serial data and ground, nothing else.
    Thanks Steveo...i'm hoping this is my problem and sorry for the elementary question but jus want to confirm that only
    "M" D29 (serial data) and "A"(ground) is what is needed. What is “B” (D20 output field service enable) used for?

  4. #4
    Fuel Injected! steveo's Avatar
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    nothing useful as far as i know

    i have an ECM on my bench right now with literally only power, ground, and serial data connected, and it datalogs and works fine.

  5. #5
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    Quote Originally Posted by toyinhawaii View Post
    Thanks Steveo...i'm hoping this is my problem and sorry for the elementary question but jus want to confirm that only
    "M" D29 (serial data) and "A"(ground) is what is needed. What is B (D20 output field service enable) used for?
    I can offer some limited information taken from the '97 LT1 code. The FSE input is an analog with value set using an external resistor to ground. There are a few different settings depending on the value of resistor used. Here are my comments from the code:

    Code:
    *************************************************
    * A/D CH6, INPUT 0: ALDL FIELD SERVICE ENABLE
    *
    * A/D CONVERTER HAS A 10K PULLUP TO +5V
    *
    * NORMAL MODE	R > 40K0 OHM TO GROUND: USE OPEN
    * ALDL MODE	R < 40K0 OHM TO GROUND: USE 15K0
    *		R >  6K7 OHM TO GROUND
    * BACKUP MODE	R <  6K7 OHM TO GROUND:	USE  3K9
    *		R >  2K0 OHM TO GROUND
    * FIELD SERVICE	R <  2K0 OHM TO GROUND: USE  0K0
    *************************************************
    The named definition of the modes was taken from info someone else provided (can't remember where I got it...)

    I have seen in the code where the FSE when grounded (that is in Field Service Mode) no longer checks the checksum/reset on invalid checksum.
    On my board there is an unused connector that was used during development for connection of a test board. FSE is also involved with that operation.
    I believe some of the modes have a timeout.

    Don't think this answers your question, but for the moment it's what I have.

    -Tom

  6. #6
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    Thank you Tom, i believe i see what you are talking about and what info is acquired when using a 10K resistor. From my current basic knowledge what i noticed during my troubleshooting and what many people on here probably already know is. Since all i had hooked up was "A" and "B" i read that a jumper wire between them would give me trouble codes. This did not work for me. but now since using the ALDL cable i found by connecting the one end to the OBD1 DLC and shorting(jumping) the 2 left pins (A short to B) on the other end(USB end) i was able to see the trouble codes flashing. Strange that i needed a cable cause in my mind i'm still shorting A and B either way. Last night i soldered in an extension wire from the Serial Data (D29) @ the PCM to the "M" plug @ the DLC plug. Tonight/this weekend i'll plug in my cable,hook it up to the laptop and access the EE HACK and we'll see what happens. i noticed on the EE HACK screen,lower left corner it had a trouble code display section. Again, with my basic knowledge it would seem that all data log would be coming from "M"(of course) and the trouble codes would be coming from "B". On a comical note, i know many on here are shaking their heads and saying No s*&^!, NOOBIE! but its all good! LOL! i love the challenge.

  7. #7
    Fuel Injected! steveo's Avatar
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    Quote Originally Posted by steveo View Post
    you need serial data and ground, nothing else.
    i'll just quote myself since it's still the truth. everything comes over the serial line. the serial line is only one pin. just connect it to your aldl cable. if it doesn't work something is wrong in your cable, ecm, or wiring. that field service enable wire isnt' something anyone uses. everything goes over that one pin. everything. every single piece of communication. trouble codes. datalogging. programming. all of it. one pin.

    i do feel like i tell you something and you don't believe me until i tell you exactly the same thing a dozen other ways so i do hope this gets through somehow

  8. #8
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    Ok, i admit and apologize, its not that i dont believe you nor anyone else that is helping me. just a little uneasy i guess of constantly running into a brick wall and these past 7 mths of soaking up all the knowledge BUT!: success,success,success! it was my fault! i didnt have the serial data wire hooked up when i thought i did. i plugged in the cable, waited 15 sec, turned it to on, hit the connect button ,it connected,saw the ee hack populate...hurray! so i hit the flash button and clicked the "downloaded the bin from the ECM" i saved it to C:program files(x86)/EEHACK, its now loaded on the "prev.bin". i did not yet flash the PCM according to instructions. i started the engine and saw the "dash" come alive. just absorbing everything now. just basic readings are(all are at idle):
    RPM= average 580ish
    spark advance=20-22 deg
    MAF=7.82 g/s(shown in red)
    coolant temp after about 10 min@ 188 degrees

    theres more but just giving these for now

    i have theses error codes:

    ERR26(CCP ELECTRICAL FAULT )
    ERR34(MAP SENSOR LOW)
    ERR97(4K PULSES CIRCUIT FAULT (VSS))
    ERR96(OIL LEVEL LAMP CIRCUIT FAULT)
    ERR95(OIL LIFE LAMP CIRCUIT FAULT)

    thanks again steveo! i know i tried your patience, this is enough excitement for tonight. i guess the next step is flashing the PCM ? thank you again all, for all your help, this was a big hurdle for me of trouble shooting this mess when it all boiled down to the main, most important item.....retrieving the data(my fault for continuously over looking it and thinking it was connected). i appreciate more knowledge if you"ll teach me...thanks all!!
    Last edited by toyinhawaii; 03-28-2020 at 07:56 PM.

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