94 Bonneville SE ODBI or ODBII

[bratfry]

The car has the 16 pin connector (ODBII type) Does that mean that it is equipped with ODBII or is it still ODBI with a ODBII plug.

If it still is ODBI, shouldn't I be able to "flash" the diagnostic trouble codes similiar to the ODBI connector using a jumper?

Was there a different standard between ODBI and ODBII, I sure hope not.

I bet its got something to do with what terminals are available in the connector. Anyone else tackled this messy issue?

Thanks for any insight before I go and start plugging and jumping.

[michael_k0]

You need a tech 1 scanner with an OBDII adapter, I think a tech 2 will also work. Regular OBDII scanners will not recognize the codes.

[bratfry]

Yes you are correct, Michael, my OBDII computer interface device didn't work on this car. Thanks,

So its OBDI, does that mean I can "flash" the codes using the old jumper method? My connector case has connectors in 4,5,8,9,14 and 16. If not, I guess the next stop is Autozone.

I would like to be able to see these codes when I'm working on the car and I am sure the GM tech 1 scanners are way out of my price range.

[Hansnet]

Your car is not obd1.

Your car is not obd2

You actually have OBD1.5.


Your only option is buying a high end scanner or paying $60+ for a dealer to scan it.


Autozone does not have the equipment to scan your car.

[michael_k0]

I don't think you can jumper it, I would be scared to try, you might fry something. Find a mechanic and buy him a case of beer or a steak dinner and see if he will stay after work, that's what I did. I replaced my computer and it runs great. Good luck

[bratfry]

Well the internet is a wonderful place full of knowledge (I think). I found many articles on GMs Assembly Line Data Link (ALDL) data stream (Diagnostic Link). I also found articles on how to build an interface to the serial port on a laptop, even some free software. So last night I build an interface using a couple transistors, resistors, a diode and few plugs. I took the “easy to build” interface because I had all the parts needed. The more complex version is probably more stable, but this is a test for me.

The software screen shots look very interesting. It has a lot more than just the codes. So this weekend I will try it out and see what happens. I will report back next week.

[bratfry]

UPDATE: 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 show 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.

You can also set it up, do a test run and replay the data of the test run for analyisis at a later time.

Gary