The Dreaded OBD 1.5 Thread. Got a '94 or 95 PCM? Look Here! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-29-2007, 01:35 AM   #1
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Default The Dreaded OBD 1.5 Thread. Got a '94 or 95 PCM? Look Here!

(warning: It is late at night and i am talking techno-babblel. So if it doesnt make sence Im sorry.)

I have decided to collect all the information I have gathered from this PCM and put it here, and let you all add to it. (Maybe eventually a formal tech-info)

The PCM in your car delivers its information in a different way. OBD 1 style (ALDL or serial data) with OBD 2 codes. I like it, because it is insanely EASY to interface to and has MORE information than OBD 1 did. It isnt as MUCH information as OBD2 but still.

The PCM is a computer with a serial port. The connector under the dash is like the serial port where it gives out all its information for you to read (and it also talks to all its systems through the same system) Standard OBD 1 gives its information at a speed of 160 baud, GM bumped it up to 8192 baud for the OBD 1.5. MOST serial ports will output this speed but not all, it is not a normal speed, therefore many USB to serial converters will also NOT work. The car also uses TTL level voltage (0-5V) and the computer uses standard RS-232 voltage (0-10V) so you need a level converter for that. The pinouts of the system as well as the circuit information and software i have found are all listed below.

This is a SMALL compilation of 4 years of research and I will add to it the more i research it. I am right now in the process of designing a OBD1 and 1.5 reader to work like the aeroforce gauge for the OBD II people.

What it is:
Quote:
Originally Posted by http://www.techedge.com.au/vehicle/aldl8192/8192baud.htm
8192 baud ALDL description

The low level logical format of GM'* 8192 baud ALDL data stream is a simple async data stream with 8 data bits, no parity bit, and 1 stop bit. This is the type of data stream that most UARTs (Universal Async Receiver Transmitter) can handle. The PC (IBM clone) has a UART that can be set close to 8192 baud (actually 8226.6 baud, using a divisor of 14 with the 115,200 Hz UART clock - giving a 0.42% fast clock, a negligible difference).
The pinout: (according to this page, we use the 'austrailian OBD1 connector pinout)' which is the OBD2 connector with a different pinout)
Quote:
Originally Posted by http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm
The circuit (I modified mine to use the MAX233 because it has built in capacitors, but a slightly different pinout):
Quote:
Originally Posted by http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm

The only software that i have found to be really worth anything is EFILive V4. Its pricey, but having all the live gauges is worth it. They offer a 30 day trial that you can access all the data with only 3 live gauges.

http://www.efilive.com/download.aspx#downloads3



Good luck! And send all your pcm info back here! (I am really looking for PIC or software programmers to help me out with the stand alone project)
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Old 06-29-2007, 01:00 PM   #2
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(bmsgaffer86 posted a pic of his "TOUCHdash" diagnostic screen in this thread:

http://www.bonnevilleclub.com/forum/...223&highlight=)
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Old 06-29-2007, 01:51 PM   #3
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http://www.obd2allinone.com/sc/toplevel.asp?cat=2
here are some more software you can use if i can figure how to upload the restof my software ill do it
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Old 06-29-2007, 02:15 PM   #4
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Ok, good.

Here'* the things on my mental list:

1. Try to find some cheap (ie free) very usable software supporting 94-95s

2. There must be, by now, a source of cheap (or even free) laptops or notebooks that would still be adequate to do the job. This syle of computer is traded in about every three years or so (and alot of them because they're just not powerful enough to handle all the latest fandangles we make them do. For auto diagnostics, almost anything made in the last seven years or so should do the job).

3. Address the problem of converting the serial signal from the enhanced cable to the USB of the laptop. (very few laptops or notebooks have the old serial port anymore). Apparently the commercial serial-to-USB dongles don't always do the job.
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Old 03-22-2010, 09:30 PM   #5
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i have a good usb converter that works well with my tunerproRT software, it has gauges is free ( nag Screen )

My car is a 95 bonny, my cable interface consists of 2 NPN transisters a switching diode and 3 resistors connected to three wires of my ALDL connector. I have no connection issues whatsoever.

let me know if you want more details
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Old 03-22-2010, 10:56 PM   #6
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Please watch the age of the threads you reply to, this thread is nearly 3 years old.
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Old 01-26-2017, 06:28 PM   #7
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Can you send me some details on this. Just got a 94 bonne the cel is in and this would def save me some cash.
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Old 01-26-2017, 10:01 PM   #8
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You do realize how old this thread is right? It'* almost 10 years old. Did you not read the welcome PM that says to read the rules? Something about digging up old threads?
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