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| 87-88 IL4 ECU Comms (Page 1/2) |
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Romsk
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MAY 05, 08:39 AM
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From what I read, 1987 and 1988 4 cylinder Fieros use 8192 Baud on pin M.
Does the Fiero just spit out data on pin M (one way) or does it have to be commanded (two way)?
I have read both because just about all the ALDL functionality has been convoluted over the years. People often speak in general terms when it comes to 8192, but on the Fiero it may have just spit out data. At one point I read that the data come out as human readable text.
I know in later years 8192 was two ways comms, but the Fiero was the first to use it and the Fiero ECUs were unique only to Fieros. So it is possible they were one way.
I have spoken with some guys that make adapters but I get conflicting info among them.
Does anyone in the Forum know for sure if the Fiero 8192 ALDL data was just one way, or does it use two way comms?
One suggested TunerPro, but you need a few conversion files to use it. And it doesn't even come with the files, you either have find them somewhere or reverse engineer them yourself.
So, I may have to borrow a 1987 or 1988 4 cyl ECM to figure this out. But if anyone has any direct knowledge of what I am asking, I would appreciate it.
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Paul Romsky
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fierosound
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MAY 05, 10:27 AM
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82-T/A [At Work]
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MAY 05, 10:58 AM
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| quote | Originally posted by Romsk:
From what I read, 1987 and 1988 4 cylinder Fieros use 8192 Baud on pin M.
Does the Fiero just spit out data on pin M (one way) or does it have to be commanded (two way)?
I have read both because just about all the ALDL functionality has been convoluted over the years. People often speak in general terms when it comes to 8192, but on the Fiero it may have just spit out data. At one point I read that the data come out as human readable text.
I know in later years 8192 was two ways comms, but the Fiero was the first to use it and the Fiero ECUs were unique only to Fieros. So it is possible they were one way.
I have spoken with some guys that make adapters but I get conflicting info among them.
Does anyone in the Forum know for sure if the Fiero 8192 ALDL data was just one way, or does it use two way comms?
One suggested TunerPro, but you need a few conversion files to use it. And it doesn't even come with the files, you either have find them somewhere or reverse engineer them yourself.
So, I may have to borrow a 1987 or 1988 4 cyl ECM to figure this out. But if anyone has any direct knowledge of what I am asking, I would appreciate it. |
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I don't know how much I can add to this that would be at all valuable, but I know that people refer to 8192 as the baud, but that's not defining the Baud Rate. As an old BBSer, the baud rate for the Fiero ECM is an excruciatingly slow 160 bytes per second, from the data output. That's quite bad, but the speed at which the ECM actually communicates with the sensors and such, is actually a lot quicker. 8192 actually refers to the UART chipset from what I understand.
I could be wrong, but I think the data feed is only uni-directional. OBD2 is definitely bi-directional, but not OBD1 (someone correct me if I'm wrong). I do know that you can easily reflash the PROMs... one of my buddies used to do this on an old 286 laptop, but it's much easier now with USB and a Temu / AliExpress chip flasher. You have to wipe it by blasting the chip's window with UV light. You have to pull the sticker off the ECM and hit it with a UV light and it will wipe it... takes a while though. But there may be a way better way to do all this. I hope someone else responds with better info.
EDIT: Sorry... I didn't see that FieroSound had responded...[This message has been edited by 82-T/A [At Work] (edited 05-05-2025).]
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Romsk
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MAY 05, 11:52 AM
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All,
Thanks for the reply. I built my own cable. I designed the Fiero GT ALDL Monitor GUI and Adapter that is now sold from The Fiero Store.
Fiero GT ALDL Monitor Adapter
My GUI currently only supports Fiero 1986-1988 V6 ECMs. I have been getting a lot of call to support all the stock Fiero V6 and IL4 ECMs.
I am in the process of borrowing a Fiero 1985 V6 ECM. That will leave just 3 different IL4 ECMs left for me to support. The 1987-1988 IL4 ECM uses pin M which is called 8192 Baud (in a common terms). The other two use the 160 Baud which I just need to verify with existing code.
My GUI supports only Fieros as it was design especially for Fieros. It doesn't need XDF or bin files or anything a user has to hunt down. My GUI will support all stock Fieros from 1984 to 1988 right from the downloaded GUI... taking out a lot of the guess work from other tools.
My Adapter will be modified to support pin M 8192 data. Right now the Adapter only handles pin E for 160 Baud Data.
My Adapter currently can set all 4 ALDL Modes via GUI control - no jumpers or switches. My Adapter also includes a Bannana Jack to test the Fuel Pump and a multi-color Status LED. The USB cable is integrated into the cable. If you add the SES signal to pin D of your Fiero's ALDL Connector, the Adapter and GUI can also read Error Codes for you... no need to count flashes, the GUI can do that for you. And it can Monitor the AFR cycling. I don't think there is another GUI and Adapter out there that does all that. Because I am a single source for the entire tool, hardware and software, I take suggestions from my users, so the tool is always improving and evolving. The GUI and updates are free for download. You don't even need the Adapter as the GUI comes with a recording file 'CS_Morning_Commute.txt' that you can play back to get the feel of the GUI before buying the Adapter. Recordings are in a simple data stream in text format that is easy to share via email. I also offer free consultations for my users. So far I have received high praise for it.[This message has been edited by Romsk (edited 05-05-2025).]
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phonedawgz
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MAY 06, 09:33 PM
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Pin E is unidirectional. That is why the 10K resistor is needed. It activates the data output. And if you noticed the data outputs about once per second with the resistor in place. And as you know the resistor alters the advance and the idle speed.
The 87-88 Iron Duke ECM uses pin M. It is bidirectional. My notes state the 10k resistor is still needed. GM later dropped the 10k resistor completely but apparently in 87 they were still figuring things out.
When you transmit on the link, you will of course get exactly what you transmitted right back. You need to ignore what is transmitted.
You will send in hex F0 56 01 B9 - The ECM will reply with a multi byte response. I will be referring to the bytes using hex. Then in that byte you need to decode the data much the same as you did with the 7170 ECM
So for example the O2 sensor reading is byte 0E . All 8 bits of that byte are the value of the O2 sensor
The TPS is byte 07 and again it's an 8 bit value
The SES indicators are in bytes 02 to 04 and all are just a single bit.
If you fire up TunerPro RT, load the .adx file for the 87-88 Iron Duke ECM and then go to ADX editor, it will spell out all of the values you are looking for.
While most of the data translates to the actual value by a multiplication factor, not all does. For the ones that translate to the data by a factor, that is indicated in the .adx data. For the data that doesn't there are look up tables to convert the data to an actual number.
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phonedawgz
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MAY 06, 09:45 PM
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Also - btw in TunerPro RT.
ADX files are definition files for scanning data streams
BIN files are the actual data burned on the PROM
XDF files are definition files much like ADX files but for the BIN file. By using the XDF file you can see what the data in the BIN file actually means.
TunerPro RT when in the BIN file edit section allows you to see what is programmed, and allows you to alter the program. So for example lets say you want a target idle of 800 RPM instead of 1,000 RPM. You could do that. Then you would save the BIN file, and then burn it to an EPROM and insert it in your ECM.
The 2732A EPROMs that are in Fiero ECMs are a pain to get to program correctly. Plus they have to be erased with a UV light. Most "used" ones fail to program correctly. So what I have done is made an adapter board that allows a 27SF512 chip to be used in a socket that then plugs into the board. I sell them here if you are interested.
https://reddevilriver.com/h...-to-gm-2732a-adapter
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phonedawgz
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MAY 06, 09:49 PM
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Actually 8192 is indeed the baud rate. Yes, a very unusual baud rate. The nice thing about the 8192 is it is quick enough to be "real time". Not the jerky, once a second update movement you get with the 130 baud.
If anyone does a 7730 ECM update it also is 8192 baud, so it scans much nicer and the idle and advance are not affected by scanning.
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Romsk
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MAY 07, 07:35 AM
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PhoneDawgz,
Great info, thanks,
So, if I can find the ADX for the Fiero 1987-1988 Iron Duke ECM, the info on how to decode it is in plain text?
I don't need the bin file.
The ADX list all the commands and responses?
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Romsk
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MAY 07, 08:03 AM
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PhoneDawgz,
So I guess I do need the bin file too. But I have no intention of "tweaking" the settings. That is bit cumbersome as you actually have to burn new PROMS.
I just want to be able to read and decode the commanded data that can come across the pin M data.
So to figure out how pin M works, I will need:
TunerPro RT
The ADX file for the Fiero 87-88 Iron Duke
It's associated BIn File
Then TunerPro RT can uses those files to show me the commands to send (in hex), what values come back (in hex), and how to convert them into units (by conversion factor or table)... got it.
I agree, some bytes are a simple conversion factor: like RPM which is 25 units per LSbit.
Some are tables: Like CTS which are based on Thermistor curves.
In my GUI, I don't have tables for the CTS, IAT Sensor, or the MAP Sensor. I took those sensors and plotted out a few points over their ranges. Then I did polynomial curve fits and created functions that takes the raw value and applies those coefficients to a 3rd order equation and it returns the units. It only take a couple of microseconds to calculate. It uses much less memory than lookup tables. But if the ADX files has lookup tables I may just do a curve fit on those as well.
My GUI won't use the ADX files directly. I will convert the data in them to DLLs that the GUI will load as it's respected ECM is selected. This way, users won't need to hunt down ADX and BIN files, the DLLs come with the GUI, all the user has to do is select the desired ECM Model number and my code does the rest. I am only interested in Fieros, so there are only 5 ECMs... I have the 1227170 DLL done, 4 more to go... 3 are 160 baud (which I understand well) and 1 for the 8192 baud.
Thanks,
You have been very helpful.
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Romsk
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MAY 07, 08:38 AM
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TunerPro RT seems to list a lot of the GM ADX files.
They also have a list for GM OBD-I data stream definitions. Those are human readable files look like C code.
But ALDL is not OBD-I, but some refer to ALDL as OBD-I. I think there is a distinction.
Anyway... this is all great info.
Thanks to all for your help.
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