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PostPosted: Sun Sep 25, 2016 12:48 pm 
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Joined: Fri Jan 09, 2015 10:27 am
Posts: 58
Location: Lowell, MA
I have been working on a small car computer built off a Raspberry Pi. It will display my WB O2 and MAP sensors but I also want it to pull data from the ECU.

I bought this cable and have not been able to communicate with my laptop. Here are a few facts about the cable:

Pin A is grounded
It shorts the M and E pins for both 8192 and 160 BAUD comm
It has a 10 kohm jumper b/t pin B and GND
It uses FTDI usb drivers

Image

The cable shows up in the device manager with the proper drivers. I open up HyperTerminal and connect to the COMM port the cable is located at. Turn the car to accessory and I am now supposedly able to see a data stream, which I do not. If I take the cable and short pins M and A characters appear, so the cable and connection are active. If I do any order of jumpering pin B there is no effect.

I tried a bunch of the free ALDL software including RhinoView without luck. I wonder if there is a difference between the cable provided by the rhinoview website...

What am I missing here? I am so close I can feel it. Thanks for any advice!

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PostPosted: Mon Sep 26, 2016 9:05 pm 
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Joined: Mon Dec 01, 2003 12:47 pm
Posts: 11667
Location: columbus, ohio
the biggest issue is that the 93 gt ecu is a "dumb" obdI design that cannot supply active data in the manner you expect it to. it's not even a primitive canbus design or pid. you will never get it to stream data the way you want it to.

the only way to see the mapping on the ecu is to read the eprom, decompile the data, and view it as a snapshot. you can change the mapping, recompile it, and burn it back to the eprom but you can never do it on the fly or in real time.

there is no active, real time data communications with the obdI ecu as there is with an obdII ecu.

the aldl port is only in place to dump the rudimentary diagnostic codes that were used by the dealerships and those codes were serial data that was called while the ecu was powered but inactive. typically you would turn on the key to power the ecu and then jumper the diagnostic switch and watch the serial data flash the cel. the aldl port only sent the serial data to the dealer's diagnostic reader which translated the flashing of the cel to a diagnostic code.

when the obdI ecu senses a code that has been set, the cel turns on. to actually read the code you close the diagnostic switch, power the ecu up without starting the engine, and count the flashes of the cel to ascertain the code. if you start the engine the ecu moves out of diagnostic mode and attends to the business of running the engine. if you leave the diagnostic switch in the on condition the engine will run with the ecu locked in open loop mode, never applying fuel trim using data from the o2 sensor.

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PostPosted: Mon Sep 26, 2016 9:51 pm 
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Joined: Fri Jan 09, 2015 10:27 am
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Location: Lowell, MA
Holy shit. I cannot believe I never came across that information in my...15? hours of internet research on this crap. I knew it was possible the port wasn't connected to the ECU, but no idea that the ECU was too dumb to give me what I want. Thank you immensely for ending this insanity.

I guess this means I go ahead and work out my own sensors. I have more research to do now.

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PostPosted: Tue Sep 27, 2016 7:48 pm 
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Joined: Thu May 12, 2011 10:08 pm
Posts: 625
Location: texas houston
Looks like you need a real Macintosh computer :mrgreen: :mrgreen:


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