I have successfully built an ALDL to Serial Port converter. Now I’m in the process of writing some simple software to interface with the PCM. Which I am willing to share! However, I’m having some difficulty figuring out how to communicate with the PCM. Could somebody knowledgeable please contact me? I have MSN Messenger, and AOL Instant messenger, or just post me some notes on the message board:

AOL screen name: weinerschizel
MSN Messenger: weinerschizel@hotmail.com

My first program I’m writing is simply to backup the PCM. I want to download the entire memory bank on the PCM to a file on the computer. Next, I want to write a program that will Flash and re-upload the file to the PCM. I am also working to make it as GENERIC as possible so those out there with any OBD-I/II GM cars can make use of it (if this is possible).

I have already viewed “Andrews ALDL GM stuff” and virtually everything linked to it. I also have a copy of the HEX definitions from the OBD I computer.

ANY HELP IS GREATLY APPRECIATED!!!!!

 

Just curious as to what kind of vehicle you're working with. OBDI is very different from OBDII. <img src="gr_stretch.gif" border="0"> And since there are two vendors out there with OBDI LT1 reprogramming software, to focus on OBDII first would be of greater general benefit...

A few questions:

1) What language are you programming in?

2) What PCM are you targeting first?

3) Do you have any documentation other than what was on my web site? <img src="gr_grin.gif" border="0"> You'll need much more, I'm afraid...

I don't have much for OBDII yet, but I'm working on it. http://www.akmcables.com/obdii.htm

Here's the gist of how it's done. Unfortunately, I don't know the commands to do this, but here's the procedure.

First, you put the PCM in to 'execute from RAM' mode. Then you load commands in to the PCM RAM, and the microcontroller takes over. Not only is the OBDII command required, but knowing Motorola 68HCXX is required (the LS1 uses a 68HC332 variant). At least, I *believe* this is how it's done, according to folks I've talk to (Steve Cole at TTS and Dave at Carputing).

Way over my head, I'm afraid...

-Andrew

 

Well... I'm targeting the OBD I PCM first as that is all I currently have to work with <img src="gr_sad.gif" border="0"> The reason for me designing these two programs first is in the future I want to get more down and dirty and if i mess the PCM up i would like to be able to restor it.

I'm going to wite a preliminary set of programs in C++ to run from the dos prompt... then make a bootable cd that can do these things cause DOS is way more stable and I don't like the idea of windows crashing when i go to flash my PCM <img src="gr_sad.gif" border="0"> that would be no good.

As far as further documentation. I don't have much <img src="gr_sad.gif" border="0"> I would like to get my hands on as much as possible. I'm a sophomore studying computer engineering though wich helps a LOT cause I can gain access to help from professors and what not.

the problems I'm encountering right now are:
1) my c++ is a little rusty <img src="gr_sad.gif" border="0"> but i'm taking a new class in it right now so this will help.
2) haven't quite figured out how to read from the serial port... but it doesn't look that hard to figure out.
3) my biggest major hurdle. I'm not sure what command to send to the PCM to get it to transmit it's memory contents to the pc.... is there code that will allow you to define what you would like to grab from the memory like which blocks and what not?? My first goal is to grab it ALL.... Every little bit of it so I can back it up <img src="gr_stretch.gif" border="0">

I did find your site VERY informative!! its great!! I will share any information I find with you. Thanks for your help!!!!!

 

Well, if you've found my web page at http://www.mindspring.com/~amattei/aldl.htm - you've found newgcar - which has C source code that can show you how to set your RS232 baud rate to 8192, shows you how to read from the serial port, etc. It compiles under Borland.

As for the commands, if you're not too proud to do a little reverse engineering, you can download the PCMread program from http://www.carputing.com - it allows you to log communications to disk. You can look at the transmitted and received commands & responses. However, you're going to need to know Motorola assembler to really make sense of these (see my post above about executing from RAM - the OBDI LT1 PCM does it too).

Keep in mind. This software ONLY works on OBDI LT1 cars, and no others. GM changes their ALDL routines for nearly every engine & platform. And OBDII is completely different.

As for 'fixing a messed up PCM', you CANNOT do that over the ALDL bus wire. Period. You must remove, reprogram, and resolder the flash memory chip. My old page at http://www.mindspring.com/~amattei/flashfix.htm covers how I used to do this (my old method). I need to make a new page. I've got 3 PCMs at my house, and at least 2 in transit, that I'll be fixing in the next few days. <img src="gr_grin.gif" border="0">

-Andrew

 

I'm actually doing something similar at the moment, although mine is geared towards a diagnositc scanner. I've been on a break over the holidays but I'm about to get back on the project shortly. I'm not too up on the older stuff (obd-I), but I'm almost positive you're going to run into many differences between the two. For starters, just the interface (VPW vs PWM) issue would have to be worked out just to get talking to the car. I'm using a PIC controller to do the comm but quickly finiding out that I'll need something a bit more powerfull to get the update rates that I want. So half way through this, I'm switching over to a moto based chip that I think will work fine. My goal in this was to 1. see if I could do it, 2. save me some money in not having to purchase an overpriced scanner, 3. maybe produce a few of these for my friends. <img src="gr_grin.gif" border="0"> While I don't think I'll be putting B&B out of business anytime soon, I think it would be usefull in doing what most of us would want out of a simple scanner. The hardest part about this project has been gathering all the info around the web. What I've been avoiding, is having to buy the SAE-3000 manual (OBD bible) for $90. At any rate, so far I've got all the simple stuff completed. Displaying RPM, O2 info, temp, spark adv, IAT, trouble codes and resetting them, etc etc.. So if anyone is interested and doesnt have one of the big brand scanners, let me know. I plan on producing a handfull of interfaces. I'm also not looking to become rich off of this. Matter of fact, probably just what it costs for materials. I think I built my prototype for $30 <img src="gr_grin.gif" border="0">

 

Oh to have the time to help on this....sigh

 

Dont know too much about OBDI but I thought I say a link somewhere maybe on www.camaroz28.com for a free scanner for OBDI, some think like freescan. Anyway you may look around and find what you are looking for.

Gary

 

[quote]Originally posted by 98blackSS:
<strong>What I've been avoiding, is having to buy the SAE-3000 manual (OBD bible) for $90.</strong><hr></blockquote>

BUY IT!!!

My copy came in yesterday and it is awesome. To get the data rate you want you'll need to put together a request that returns multiple piece of information at once. This book tells exactly how to do it and has examples of the request/responses.

I'm working on a OBDII scan tool for my palm pilot right now.

What I really want to know is how to make my windows roll up and down like this thing does:

http://www.topdowntech.com/productInfo.html

<img src="gr_grin.gif" border="0">

OBDI stuff

On the original subject I wrote a 94-95 scan tool in perl using linux. It was a fun toy but I never really got the timing exact so my frame rate was only 10-12 fps.

Just so you know, LT1 Edit and Tunercat both download ALL the memory that is addressable by the pcm. There are two parts of the 94-95 pcm, the T side and the E side. $0 to $1FFF are memory, $2000 and up is the flash prom on each side.

When you say OBDI, I assume you mean the 94-95 lt1 f-body pcms. OBDI is not much of a standard when it comes to stuff like this so each pcm is going to be a bit different in its own way.

My '93 LT1 doesnt flash so I lost interest in doing that on my own.

Eric

 

I've been thinking about it Eric, and I may just have to. What I basically have now for info is bits and scraps. I've had to figure a lot out on my own as far as the calculations (yeah, even the OBD generic PID's). I'm not even sure how much info is out there on the GM specific stuff. Did you buy it directly from SAE or somewhere like Amazon?

 

I bought it direct from SAE. 400 pages. $100 shipped 2 day UPS.

Eric

 

Andrew:

i got interface with the serial port figured out... I'm just having one last trouble with it though. I can't get the right library to allow me to use outp and inp tags... I'm runing GRRRRR stupid friggien riggen, microsoft visual c++. Were did you find the library to do it with?

Thanks for the help!

 

Download this. It may help. <img src="gr_stretch.gif" border="0">

ftp://diy-efi.org/incoming/95camaro.zip

-Andrew

 

I have free ALDL Microsoft VC++ (although it is written in C) serial comms console based application including source code.

Also a free OBD-II VPW software driver that requires no hardware interface (save the two wires to connect) includes source code. It's a bit flaky due to the standard PC (DOS and Windows) not having a much of a concept of what "real time" actually means. Trying to get DOS to calculate timings as small as 40 microseconds is a big ask. But it works on some platforms and I can get trouble codes out of my LS1 using it.
If anyone wants to have a go at making it more stable please do. I don't have time right now, but I'd love to see it working properly.

These can be found at www.blacky.co.nz/free

Plus Carbytes V2 (also free) which, as well as being a scan tool, allows you to download and save your ECM's memory.

Regards
Paul

P.S. Hi Andrew M. (aka Camaroholic) if you ever get the OBD-II hardware working I would be interested in porting EFIlive V5 to use it.
Too many lists - not enough bandwidth <img src="gr_stretch.gif" border="0">

 

Keep all this stuff going and I can see up putting up a Electronics Forum. Very interesting stuff!

 

I looked into this very thing a year or so ago. It's really disturbing the prices some people charge for computer reprogramming. I thought it would be cool if I could come up with something for my club, but I didn't get very far. I can see it taking up a decent amount of time.

I still have all my links saved so maybe they will be of use to you.

Carputing
ECU Software
GM P4 ECM Crossreference
How to hack GM ECM
DIY EFI
Ruse Electronics (Interface Cables)
LT1 Edit
TunerCat
Universal Cross Disassembler

 

66impalaLT1-

Have you seen the CJ II scanner for the Palm OS? You can see it at www.etoolcart.com I've talked to the guy about a GP of sorts- it was priced about the same as Atap.

JEFF
Here is the CJ II:
http://www.etoolcart.com/product.asp?3=9

[ January 17, 2002: Message edited by: JJH98SS ]</p>

 

Yes, I've read about it before. Its not exactly what I want to do.

Eric