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Thread: Funny adventures in electrical engineering

  1. #201
    Join Date
    Jun 2019
    Location
    Houston
    Posts
    9
    Ok so there's a possibility that the firstmost pin on the 10 pin connector goes to INT2/P72 but for the most part the others seem to go nowhere... 2 others seem to go to a power switch of some sort? (they seem to lead to a chip called SE191 which as best as I could find is some sort of power switching thing, but idk) P72 doesn't explicitly say serial anywhere but Im not familiar with the language used in the manual so I'm not sure.

  2. #202
    Join Date
    Jun 2019
    Location
    Houston
    Posts
    9
    Slight update. Some pins from the bottom seem to go to the unidentified chip, which is unfortunate because I have no clue what it actually is. I hope the maps aren't on it... Some pins seem to go through the middle of board the to somewhere as well or it seems that way using a flashlight.

  3. #203
    Join Date
    Nov 2012
    Location
    Brampton, Ontario
    Posts
    1,487
    So the typical toyota ecu from this era (well, more so earlier given my experience) is one microcontroller to run the engine, one microcontroller to run the transmission.

    To validate some of this you can chase out the pins on the micro through some of the other components to the particular sensors and actuators on the engine. check the ecu pinout and find out what the injector and igniter outputs are, then follow them back (use a multimeter with a continuity beep). Inputs will likely be buffered by some resistors or an IC, outputs will be buffered by an IC or transistors. It helps the most if you're able to power up the computer on a desk and feed it some fake engine signals with a function generator, tracing out the inputs and outputs with an oscilloscope. You could also use the vehicle itself for this but thats significantly more cumbersome.


    I recalled finding a subroutine once in these computers that read out an address given a request for one. that way they could build a scantool that just dumped data from the ecu. chances are that's what that port does.

  4. #204
    Join Date
    Jun 2019
    Location
    Houston
    Posts
    9
    Ok, that makes sense. The 9000 chip has a 16mhz crystal and the other chip has a 8mhz crystal, Im guessing the slower one runs the auto trans? I will check the ecu pinout and see what pins go where to confirm its the right chip though.

  5. #205
    Join Date
    Jan 2016
    Location
    Russia
    Posts
    20
    It's part of OBD specs that ecu could output particular address contents, but it works for restricted address range. It helps scan tool determine what data sets and active tests are supported by a particular ecu
    Processor itself, on the other hand, can output its memory contents, but you have to run it from external memory first

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