1994 error code question

I've read through the board quite a bit and have seen the link to the error code info for my 1994 Suburban 5.7L TBI truck. So I'm aware that I may or may not need a scanner to get error codes (because '94's may or may not need a scanner / reader).

I DO have the A and B terminals, but when I jumper them I don't get any flashing of my SES light.

My question is: How do I know whether this means I don't have any stored error codes OR does it mean I can't get the error codes without a scanner?

In other words, what happens with a truck that doesn't require a scanner when you jumper the terminals and don't have any stored error codes?

The only thought I had about this (without just buying a scanner) is that I could intentionally create a code and then see if I can read it. Problem is, I don't know what to do to create a code.

????

Thanks for any thoughts.

You should get a code 12 no matter if there are other codes or not.

See http://www.troublecodes.net/GM/

//2000CAYukon

You should get a code 12 no matter if there are other codes or not.

See http://www.troublecodes.net/GM/

//2000CAYukon
I think I get what you're saying, but maybe not.

I'm familiar with that page but I'm not quite sure what it (and you) mean, exactly.

At the bottom of that page is a table of "GM Generic Codes" which appears to be further clarified by the heading "Without Onboard Diagnostics (OBDII)."

I just don't quite understand what that last heading means unless it means that the codes listed in that table only apply to vehicles which do not have OBDII diagnostics. If that's what it does mean, then I guess it makes sense because I think that OBDII codes are not simple 2-digit codes. Which means that the table is a table of generic codes for OBDI vehicles only (meaning pre-1994 GM vehicles and maybe some 1994 & 1995 vehicles).

It's the "Without Onboard Diagnostics" part that I find a bit misleading. Because even pre-1994 GM cars have onboard diagnostics. It's just that they are OBDI and not OBDII.

So....... it would seem that the table is giving generic OBDI codes only.

And I think what you are saying is that IF I have OBDI, then I should get a code 12 no matter what.

And that if I don't get a code 12, then I guess it means I have OBDII.

Correct?

So I take it that you think I have OBDII, and thus need a scanner to read the codes.

Correct?

Unless, of course, I'm somehow just not jumpering the A & B terminals, which is always possible but I think not the case here since I did it at least three times and with a couple of different wire jumpers.

There are some vehicles that the 94 and/or 95 model years require a scan tool that is specific to that model year. An example of this is 94/95 Impala/Caprice. They are OBD-I but could not be read by jumpering A and B terminals.

I am not aware that 94 GM Trucks had this issue. I believe that your 94 is OBD-I and you should be able to jumper A and B.

You should make sure that the fuse to the OBD-I port is not blown. Might be the same fuse as the cig lighter.

//2000CAYukon

...I am not aware that 94 GM Trucks had this issue. I believe that your 94 is OBD-I and you should be able to jumper A and B...//2000CAYukon
That info is in the link that you provided. I already was aware of that link and its info and that's why my original post was worded as it is. It says in there: "NOTE: Some 94 & 95 models that DO have the A & B terminals still require a scanner."

So I was aware of that fact, which is why I stated that my truck does indeed have both the A & B terminals. Apparently, some 94 & 95 trucks don't have the B terminal, as the link also notes.

But I do appreciate your effort in making me aware of the link.

I also appreciate your advise as to the fuse issue. I'll make sure to check that. Also your advise as to the scanner that might be required; namely, that it might be specific to my truck? If so, I'll be sure to get one that will definitely work on my truck.

So as it stands now, I'm still not sure if my truck requires a scanner. I guess I need to know from someone who has OBD-I and who will confirm that when you jumper the terminals, you always get at least the 12 code. That does seem to make sense since that code simply means you're "in diagnostic mode" (12 = diagnostic mode).

If that's the case, and I just can't get it (after making sure everything else is in order), then I guess I'll have to conclude that I need that scanner if I want to check my code situation.

Just curious, which style connector do you have? Is it OBD-I or OBD-II?

//2000CAYukon

I'd have to say it's OBD-I. It's a 12-pin connector, same as is shown on that "GM Trouble Code Info" page you linked. However, if you look at the connector shown on that page, mine has terminals A,B,C,F,G & H only. It's under the dash on the driver's side.

I believe OBD-II connectors have 16 pins.

The wikipedia article on this subject says that my truck likely has "OBD-I.5", although it was never really referred to as that.

Edit: HOLD ON! NOW I get it. I was jumpering the wrong terminals because the connector on the page you linked wasn't as clear as one I found elsewhere (which I'll post once I figure out how to post links).

This means that the terminals I have are actually A,B,G,H,J & M. The terminals I previously thought were A & B are actually G & H. And vice-versa. Basically, I had the connector upside down.

So now I've jumpered the correct A & B terminals and indeed I'm getting the "12" code. And only that code. Over and over. So I guess there are no other stored error codes.

Here's the link that more clearly shows the terminals on the connector, and also has other good info:

http://www.aldlcable.com (http://www.aldlcable.com/)

I'm gettin' there.

Code 12 by itself means that no codes are stored and the Check Engine Light should be off during normal operation.

//2000CAYukon

Those OBD 1 vehicles often lose the code when you shut the key off soooo when the CEL pops on pull the code immediately without turning the key off and see what ya get.