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New Info: 1995 non-OBD-II 16-pin

10-26-2004, 01:02 AM
Ran across the following book in Barnes and Noble today... Suprisingly it was rather up-to-date and contained some hard to find information. I was impressed.

The Haynes Computer Codes and Electronic Engine Management Systems Manual
Haynes Techbook Series Number 10205
ISBN 1-56392-232-0

This book gets deep into the grit of obtaining error codes on all sorts of vehicles, including some OBD-II complient vehicles where the manufactuer has left a way for the non-mechanic to get the error codes without a OBD-II tool. -- It talks about some Fords where you can't use the diagnostic port without a scanner, so you climb under the vehicle, pull apart a harness, short two wires for 2 seconds, take the jumper off, short the wires again, and then it will blink the codes. I was definately impressed.


When I looked up the code retrieval for GM Domestics, I found a special note relating to 1995 GM vehicles. The move to OBD-II standardization started in 1994, GM started phasing it in during 1995. However, those 1995 vehicles came in different flavors depending on the vehicle and what part of 1995 it was manufactured.

There are at least groups of 1995 vehicles which have a non-standard 16-pin connector.

The first group of vehicles still contain an ECM, rather than a PCM, and thus still report codes via flashing the MIL/SES light. The 16-pin connector is not a DTC connector, but is rather a modified ALDL connector. (The 1995 S-10 is the example used in the manual.) These vehicles are NOT OBD-II complient and will not work with OBD-II scanners.

The pin out of the 16-pin connector for these vehicles looks something like this:

\ X | X | X | 4 | 5 | 6 | X | X /
`\9 | X | X |12 | X | X | X |16/

Where: X denotes pins that are unused.

Short 5 (ground) and 6 (test) to recieve ECM error codes via the SES indicator.

The IMPORTANT thing to know about this group of vehicles, is that you can still get the old style error codes from a blinking Service Engine Soon light. To do so, you short pins 5 and 6 on the above diagram.

This where the information I gained from the Haynes code manual stops, and I start babbling about my car.

The second group of vehicles have a different pin out than above. I know they exist because my 1995 LeSabre is one of them. Judging from the wiring, plugs, and number of terminals, the car uses a PCM not an ECM.

I've also refered to component location diagrams for the VIN L engine (3800 SFI V6), and it identifies the module location as a PCM. Those diagrams also refer to a DTC connector, rather than an ALDL connector on other diagrams for different VIN codes / Body Styles of the same year.

The location of the contact differ from the above plug. I have tried every possible pin to ground (after a lot of time with a multi-meter). No combiniation intializes the codes-by-blink mode, which is also something that is characteristic of a PCM.

My guess is, this group of vehicles was installed with a 16-pin DTC connector believing that they would be OBD-II complient. Then the standard either changed, or due to some political thing all the pins had to be re-arranged, etc. The 16-pin on my 1995 LeSabre looks like this:

\ X | X | X | 4 | 5 | X | X | 8 /
`\9 | X | X | X | X |14 | X |16/

X = Unused
4 = Chassis Ground (black)
5 = Signal Ground (black/white)
8 = Door Lock Programing (short to ground, 4 or 5) - (black/white)
9 = Unknown, Hot w/ Ignition (tan or pink or orange)
14 = Unknown, Constant Hot (blue or navy or purple)
16 = Battery+ Constant (red)

(As you can tell, I'm color blind. When all you have is a flashlight, it's a little hard to pick out the colors.)

My bet is that if I move pins 9 and 14 to pins 2 and 10 (the standard OBD-II placement for GM vehicles) that I can get a OBD-II scanner to read the codes.

However, I could be totally wrong. The Vehicle Emission Control Information label under the hood states "OBD-I Certified." Now I'm not sure if that's because they put the wires in the wrong place, or if because something else is even more screwed up.

BTW- More good information everyone should know. You can find out if your vehicle is OBD-II compliant by looking at the Vehicle Emission Control Information label on the top of the radiator shroud. It will state "ODB II Certifed."

And just in case anyone is curious, the OBD-II Certified standardized 16-pin DTC plug is arranged like this:

\ X | 2 | X | 4 | 5 | 6 | 7 | X /
`\X | 10| X | X | X | 14| 15| 16/

X = Unused
2 = SAE J1850 Bus+
4 = Chassis Ground
5 = Signal Ground
6 = CAN High (SAE J2284)
7 = ISO 9141-2 K-line
10 = SAE J1850 Bus
14 = CAN Low (SAE J2284)
15 = ISO 9141-2 L-line
16 = Battery+

NOTE: Depending on which type of vehicle you own (and which protocol is uses to transmit information), you will have a different combination of pins 2, 6, 7, 10, 14, and 15. Pin 4, 5, and 16 are mandated as part of the OBD-II standard.

As far as pins 2, 6, 7, 10, 14, and 15 are concerned, these are the protocols and manufactuers that use them:

SAE J1850 VPW (Varible Pulse Width modulation)
-Pins 2, 4, 5, and 16 are used, but NOT 10.
-GM cars and light trucks

ISO 9141-2
-Pins 4, 5, 7, 15, and 16 are used.
-Chrysler, ALL European imports, and MOST Asian imports

SAE J1850 PWM (Pulse Width Modulation)
-Pins 2, 4, 5, 10, and 16 are used
-Ford vehicles

Some of the detailed information was taken from . There are some other sites, but this link sums a good bit about what's out there in one page. (The OBD-II Home Page - Sponsered by AutoTap) is by far the biggest deposit of information relating to the OBD-II standard that I have found thus far. Check it out if you're interested.

If you've made it this far, I wish to congratulate you. I expect most other people hit the back button about 20 minutes ago... I know I almost did. Hope this information was of some help, and that it was worth reading all this.


10-26-2004, 01:51 AM
heres another little tid-bit i learned today, my 95 regal 3.8L has OBD-2, rear O2, but a 12 pin connector. I hooked up a scantool and got a 3 digit DTC, as you know, OBD1 codes are 2 digit and OBD2 codes are one letter + 4 digits. the code was 670, i looked on ALLDATA and matched it to P1670.

10-27-2004, 08:45 AM
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Scott Leavenworth
03-06-2005, 01:07 PM
I am on the same quest as you with my 95 Riviera. Same situation exactly with the exception that my pinout includes a contact at pin 11. My Riviera is supercharged. Could that be the difference?
I read in another post that a Riviera owner got good codes when he used another obdII code reader of a different make. Mine is an Innova 3100 and it only gives me error reads. I hope you are still pursuing this problem and will check back for updates. If I learn anything new, I will post it here.

05-17-2005, 01:24 PM
I have been doing similar experiments with my 94 Pontiac. It has a 16 Pin ODBII type connector but really is ODBI. Probably ODB1/5.:) I build a two transistor interface unit that converts the serial data from the cars computer to a laptop. The ground is pin 5 the serial input is pin 9. Some units show the ground at 4,5 or 6.

I found a program call Carbytes V2 and studied. I identified my ECM as a 16183247 using replacement data. I downloaded the data stream definition specifications that shows what the ECM modes are and also what the data stream bytes are. An example byte 26 is battery voltage, byte 3 is coolant temperature, byte 58 is malfunction flags.

The program allows you identify each byte of the stream and convert it to car talk. It’s a real job and it works, almost…

What I have to do is sent a serial of commands to get the data (without all the other junk on the serial bus called chatter, there is a lot more than the ECM data being discussed on the serial bus) . Then the defined information I want to look at is displayed. I repeat the operation every X ms to get new data.

I think my little two transistor circuit is not up to the task. It times out and give me many errors. I am now looking to purchase a IC type interface made with a MAX 232 or 233 chip designed for serial applications.

This same setup will work with ODBI also. Of course every ECM has a different data stream and the ODBI requires a manual starting of the stream using a resistor. The old GM standard seemed to be 160 baud serial rate, mine is a 8192 baud rate.

Love the standards that the automotive companies use. Hope this helps, will update when I get my new interface built and hopefully working.

Of course you can purchase software and interfaces already made. The costs I see are around $300. I expect to get this working for under $100. That’s all I paid for my ODBII setup using a laptop. And its fun to learn.

For you tuners out there, use your imagination…..If you can get serial data, you just might be able to get the ECM control data and maybe change it. Not me…I have enough problems keeping these things running good.


05-17-2005, 02:29 PM
With the help of the service manual, I figured out the function of the 16pin DLC pins of OBD-I cars.
The DLC of my 1994 Park Avenue is identical to the 1995 LeSabre one, posted by avatar307:

\ X | X | X | 4 | 5 | X | X | 8 /
`\9 | X | X | X | X |14 | X |16/

The following are the colors and functions:
X = Unused
4 = Chassis Ground (black)
5 = Signal Ground (black/white)
8 = Door Lock Programing (short to ground, 4 or 5) (black/white)
9 = Data Line (tan)
14 = E&C Data Line (dark green)
16 = Battery+ (orange)

Data Line is the main Data Line (8192bps most probably).

E&C Data Line connects the A/C components (HVAC programmer, AC main controls, AC passenger controls) and the radio in a daisy chained manner. On cars without dual AC, there's only the connection from the radio to the DLC. It's obviously the bus that the components of the dual AC system use to communicate. Not sure what the connection to the radio is used for though....
However, I don't see any other use of this E&C line, so for getting data and error codes off the vehicle's PCM, pin 14 is irrelevant. Pin 9 is the important one.

05-17-2005, 07:23 PM
Good post avatar but when you spoke about the S-10 trucks you made an error. In the 95 model you had 3 different systems.

1. OBD 1 with 12 pin and a PCM. DLC.
2. OBD 1 with 16 pin DLC and a PCM.
3. OBD2 with 16 pin DLC and a VCM.

OBD2 cars are easy to spot. If the engine computer is under the hood you have an OBD 2 car if the computer is inside the passenger area youi have an OBD1 car.

The reason you see a mix of the 12 pin and 16 pin DLC's was during the built when the factory ran out of the 12 pin they went to the new mandated DLC.

07-07-2005, 06:11 AM
E&C Data Line connects the A/C components (HVAC programmer, AC main controls, AC passenger controls) and the radio in a daisy chained manner. On cars without dual AC, there's only the connection from the radio to the DLC. It's obviously the bus that the components of the dual AC system use to communicate. Not sure what the connection to the radio is used for though....

Not that I think it will be helpful to anyone, but as far as I have figured out, the connection to the radio dims the digital display of the electronic climate control system. It uses (as I recall) a fixed frequency, variable duty cycle signal that causes the brightness to go from fully bright (if you disconnect it) to completely blank (if you connect it to 12v constant).

This only becomes important when you replace the factory radio. The factory radio is what dims the display when the headlights come on. (I don't know why they did this.) So if you have an aftermarket radio, you have to build a module to dim the display or else you have a really bright light on your dash at night.

07-08-2005, 02:38 PM
My 1995 Buick LeSabre is OBDI compliant but with a IBDII connector. How can I obtain the computer codes to find out what is wrong with it?

07-31-2005, 02:45 PM
Which pins should I short to receive trouble codes?

08-02-2005, 07:55 AM

Re-read this entire post carefully and you will understand that you really can't short anything and get the codes for this type of OBD. If fact you might wreck something in the computer.

Options I can think of, 1-buy the correct code reader, expensive 2-Stop at AutoZone and see if they can read them, cheap or 3-take it to a repair shop, maybe expensive.

Good Luck

05-31-2007, 02:49 PM
To read the codes a GM "Tech 2" reader does the job. I this is an odd-ball OBD system and as of I can tell that type of reader is the only kind that works. A standard OBD1 reader does not fit and as far as I can tell there is no adapter, and if there were it may not even work. A standard OBD2 reader fits, however, can not read anything. Tech 2 readers are at GM dealerships. Dealerships usually charge about $100 for 5 minutes work, so hopefully you know someone! Or you could buy a Tech 2 on ebay for about $1500 :-P.

05-31-2007, 03:13 PM
Welcome to AF, please check the dates on the threads before posting, this is 2 years old!

05-31-2007, 08:08 PM
Posting in closed or outdated threads :nono: (

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