I've been having quite a few issues with my car, most recently being the ABS kicking on. I did have leaking brake fluid, but after that was repaired, it is still happening and is thought to be possible a wheel sensor issue.

I was planning on using the paperclip method to pull the codes from my (assumed) OBD-1, but when the clip didn't seem to fit right and it looked like I could see through most of the socket and then could only feel and then see 2 wires in the back, I was sure something was amiss.

A little research confirmed my fear that it was OBD-1.5 and was wondering what my options are (hopefully with what I have on hand).

It seems like the top black wire (A) is ground and the bottom beige/tan wire (M) is the serial wire. I keyed my car in the on-position and my multimeter showed 4-4.3V between the wires and was wondering if that is the limit the signal would be at.
IMG_20140808_105706 - Copy.jpg

I was hoping I'd be able to manually connect wires to a UART device connected to my computer via USB and then use a serial terminal like Putty to call out to the OBD and pull the codes.
FT232 USB UART Board Type A FT232R FT232RL to RS232 TTL Serial Module Kit New | eBay

I'd hate to have 12V shoot back through the UART frying the serial module and my computer.

 

No joy.
IMG_20140809_170839.jpg
Black wire GND pin from car (unattached) to USB UART GND
Beige (bidirectional signal?) wire from car (unattached) tied to TX and RX on USB UART through breadboard (could use tape or twist the wires, but I had a BB on hand).

IMG_20140809_171117.jpg
Car ignition switched from off to on position.

IMG_20140809_171313.jpg
Black wire GND pin from USB UART to OBD GND pin "A".
Beige wire from breadboard (USB UART tx&rx) to OBD signal pin "M"

OBD_Capture.GIF
Using Putty serial terminal 8192 baud 8N1.
Output repeated over and over (should have kept the log to see what it began with).

I question whether the output was this way because I didn't use the power jumper on the UART board.
When I tested the board alone, jumping RX and TX (for echo purposes), I would get garbage (if anything at all) when I did NOT have a jumper on the 3.3V/5V selection pins. When I DID jump the 3.3V pins, it would echo exactly has expected. My understanding of that is because there was no power being supplied from anything else (eg, the car).
So then I question whether that is also the reason for the garbage from the car. I was expecting the car signal to be the power supply, but that may have been irrational thinking.
I was going to jump the 3.3V pins and give it another try, but before that happened, the data stopped flowing. I was talking with someone while doing it and think I missed my opportunity.
My car battery is ultracapacitors, wired in series and I think it just drained really quickly. My multimeter showed <1V on it, so now I've got my solar panel hooked back up to it and I'll give it another go with the jumped 3.3V pins once the ucaps are charged up.

 

WOW, no wonder my ucaps drained so quickly yesterday. My MM was showing >6A draw when my ignition was in the "on" position (not starting my car).

 

Because the output contains NULL characters, I'll include the HEX:
58 02 20 20 9c 0a 58 02 20 20 9c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 6f 20 20 20 20 56 5e 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 50 75 54 54 59 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 50 75 54 54 59 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 17 15 55 eb 0a 58 42 20 20 5c 0a 58 42 20 20 5c f0 56 f4 c6 0a 58 42 20 20 5c 0a 58 42 20 20 5c 05 5f 42 20 20 37 72 20 20 20 20 56 5b 55 d6

and now the ASCII version of that HEX output (just in case the nulls kill the following output):
X œ
X œðVôÆ
XB \
XB \_B 7o V^
XB \
XB \ðVôÆ
XB \
XB \_B 7r V[PuTTY
XB \
XB \ðVôÆ
XB \
XB \_B 7r V[
XB \
XB \ðVôÆ
XB \
XB \_B 7r V[PuTTY
XB \
XB \ðVôÆ
XB \
XB \_B 7r V[
XB \
XB \ðVôÆ
XB \
XB \_B 7r V[Uë

There's a lot of repeating over and over. I never initiated the communication and was expecting/hoping I'd be using the typical serial AT commands to pull information rather than it all being dumped.
I'll try other various baud rates, but am not expecting anything good to come of my tests.

To deal with the 6-amp power drain while the ignition is in the "on" position, I just hooked up ATX 12V and GND pin wires from a computer power supply I had, directly to the car terminals (bypassing the ucaps/battery because something scary happened connecting to my charged ucaps).

 

Nothing good came from changing the baud rate.
I thought maybe the rx and tx tied together might have been starting something bad and removed the TX pin from my USB so all the car could to was TX and my computer RX.
My thinking was maybe the car was looking/waiting for a certain message before starting and was starting prematurely with the TX tied in.
Still no good. Even without the TX from my computer, the car was still flooding my serial port with (seemingly) garbage and not waiting for a special tx.

I've gone to the GM site and transferred to the Chevy site and contacted them so hopefully they can give me more information.
I've seen references to ELM327 and don't know if that chip or whatever is the key.

 

what exactly are you trying to accomplish?

pulling the codes? scanning the car while driving? flash the pcm with a performance tune?


did you try a regular obd2 scan tool like the ones Autozone and other parts stores carry?


basically what you have is an obd1 pcm (sort of) with an obd2 connector under the dash. i would assume that the scan tool from autozone will pull your codes for you.

 

Wait, not teeth, pulling codes.
In the end, from the beginning I was only wanting to pull codes, but I will say that while I would still be satisfied just pulling codes, my computer-geeky side would like to dig in a little more and have my computer chat with my car OBD-style.

I have NOT used any scan tool as of yet thinking that none of them will work. In my first post you'll see me mention the only 2 pins in that socket and from the socket diagrams I've seen online, none of them will do it.

You can go ahead and assume wrong with the Autozone in my area. I just called them out of curiosity (considering Advance Autoparts never even heard of my OBD layout) and they said they didn't have anything that would work and the guy did sound knowledgeable. I even mentioned this forum and my thread and my hope to get a reply from Chevy.
He said that at that time, they pretty much did what they wanted back then and only a special scanner would do.
He was mentioning $250 scanners or going to a pro place to do it for $70. Tuffy Auto just "fixed" my rusted brake lines (after Farm and Fleet did a different part of the rusted brake system in 2009), and would charge ~$100 for the diagnostic alone. Even then, that doesn't say they'd get OBD results because the diag would entail finding out why my antilock light stays on and sometimes the ABS traction kicks in out of the blue. It's believed to be a wheel sensor issue.

Thanks for chiming in. Hope someone can lead me in a DIY direction. After researching on this forum, I saw mention of the How-To section and I didn't see it at first, but boy is it bang on. I too have the hazard light issue for one, so I'll be keeping that at the forefront of my mind.

 

in my experience, do not listen to what the counter person says at any parts store, i do my own research for a reason, and some minimum wage car expert wanna be isnt going to tell me any different. but he may be right. i believe there is an obd2 scantool out there that DOES work but not at all common.

but here are some links to other forums that are trying out things that you might be interested in....

Homemade Actron CP9110 cable for '95 Bonneville : 1992-1999

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

OBD 1.5

 

I will listen to anyone, but take anything anyone says with a grain of salt. I'm very open-minded and take in anything and dismiss anything that doesn't pan out.

Heh, I actually had seen the last two links during my research, but not too sure I saw the first link. I probably dismissed it because of the schematic that showed in Google Images.
I am only dealing with 2 pins so that is the kicker, not knowing whether it will be read by a v1 or v2 scanner or if GM did their own thing.
There are also dead links in those threads like brian89gp.
I will say, I am MOST intrigued by OBD 1.5
"Ive given up and Im upgrading my harness and PCM to ODBII to save myself the pain.", but the link for that fails too.

I also contacted Peter from GM 8192/160 Baud ALDL Interface which I think I had gotten from the "Dreaded OBD" link but haven't heard back yet.

However Jim from elmelectronics.com said "...we're not really up on the OBD I protocols..." directing me to OBD Diagnostics whom I will attempt to contact next.

"cac@chevrolet.com" said:
*****
> We appreciate the time you have taken in writing to us regarding your inquiry about the OBD socket on your 1995 Monte Carlo Z34.
>
>
> We recommend you to contact General Motors Heritage Center with telephone numbers: 586-276-0693 or 586-276-0691 or via their website at GM Heritage Center - Home. This department handles concern for; Vehicle Information Kits Contains basic specifications, equipment availability, and in some cases, owners and service information.
>
>
> You may also contact GM Media Archive at 734-462-5543, extension 163 or their website GM Media Archive. This department may be able to provide, Build Sheets / Vehicle Invoices & photograph / research services for car enthusiasts. Sales, Service, and Press literature (Ex: Possible copies of original sales literature, press releases, product description / assembly manuals, options catalog, diagrams, paint color / trim package, general history info on the vehicle).
*****

Then "gmhc@gm.com" from Chevy's GM Heritage link said:
*****
I don’t know why you were referred to us. We are an archive and no equipped to give technical advice. All we would have is the service manual.
*****

At least the GM and Chevy had replied. I expected to be ignored, so props to them for at least that.

 

Ding Ding Ding! We (may) have a winner!

After following Jim's advice, I contacted the folks at obd2allinone.com
The first reply from them was very bare saying just buy the correct cable and tunerpro, but then Ken also replied with a much better response:
*****
The 1994 and 1995 versions of the GM OBD1 did not have the A and B pin trick to read codes. These were transition years for them. The way these communicate is by data packet. What you see is correct, the vehicle spits out data packets regularly - no request is necessary from the PC. The ELM 327 does not work with this system.
Our product is designed specifically for this:

OBD Diagnostics, Inc. - OBD2 All-In-One Scan Tool w/ USB

Use software such as scanner pro to read the data stream.
*****

I had seen that cable before in my searching, but wasn't sure if it still would work with all of the pins on it and only 2 on my socket.

But because it looks like I was already going in the right direction with my setup, I'll be giving it another try and see if tunerpro can parse the output I capture in a log file.
Since all it does is spew data, I won't be tying in the RX and TX either. I only need to RX the car's TX.

I wish I already had a sample saved of the log when I tried capturing without the lines tied together, because putty looks like it may have been responding/injecting some stuff itself (thus, the "PuTTY" in the output above) and I'm sure that won't fly with any parser and I couldn't be certain what to cut out in order to clean it up.