89 OBD1 questions

[CarolinaC4]

Hey Guys,
I have tried to get the codes by grounding pin B to A, nothing happened..no codes. A is ground, I checked it is grounded. B should be the pin that when grounded displays the codes if present. I did have a odd occurance when i grounded B; the radiator fans came on, thats not right is it? Additionally there is 4 volts on pin B, thats not correct is it? All of this was observed with the key in the on position, when off the fans did not run as well as there was not voltage present on pin B. I would appreciate your thoughts on this. And no I do not have a FSM yet, I'll get one this week. Thanks in advance for your positive feed back

 

[djsroknrol]

The fans came on in my '84 as well....my wife's Cutlass does the same thing. I think it's pretty much a standard occurence.

You did follow the proper steps like putting the jumper in with the key off? Is the SES light lit when you turn on the ignition? Did you get the code 12 3 times?

It might be your're seeing an intermittent code...those do not get stored; in that event, there are no codes stored.

 

[CarolinaC4]

I tried this a while ago, sorry if I am repeating myself.
I tried to recover the codes (if any) from my 89 by grounding the Pin B to A. No codes...nothing. Not even code 12 which should be shown.
When grounding pin B to A with the switch on,the radiator fans come on. Additionally I am showing 4 volts on pin B with the switch on. I do not have a FSM yet; I will this week. The car is running rough and I would like to check for any codes if present, but not having much luck. I appreciate any help, thanks in advance.

 

[vetteoz]

No codes...nothing. Not even code 12 which should be shown.
When grounding pin B to A with the switch on,the radiator fans come on.

The fact the fans come on shows ECM has correctly entered diagnostic mode ;
If fans don't run when the ALDL jumpered , you have a problem

Does the SES light ,light up with the other warning lights in the DIC as it should when the key is 1st turned on?
If not the bulb is probably blown
Swap SES bulb with a known working one from one of the other displays

I Additionally I am showing 4 volts on pin B with the switch on.

Irrelevant ;
A-B is only a means of putting ECM in diagnostic mode ; nobody measures that voltage ( prob a data signal anyway )

 

[Hib Halverson]

Since you don't currently have the FSM, see the article at Corvette Action Center | Tech | A Dose of Digital: Part 1 - The Basics - Page 1 of 5 for background info on OBD.

Next, I'd rule-out a bad ground at the DLC by conecting Pin B to a known-good chassis ground (rather than pin a) then turning on the key and seering if the MIL flashes.

If it doesn't you need the service manual's diagnosis information for a no-code-12 situation.

 

[CarolinaC4]

The fans came on in my '84 as well....my wife's Cutlass does the same thing. I think it's pretty much a standard occurence.

You did follow the proper steps like putting the jumper in with the key off? Is the SES light lit when you turn on the ignition? Did you get the code 12 3 times?

It might be your're seeing an intermittent code...those do not get stored; in that event, there are no codes stored.

I put the jumper in with the key off. I may have a blown light bulb. Should the light come on when i normally start the car? If so I haven't seen it, so I may have a bad bulb. One more thing to check.

 

[vetteoz]

Should the light come on when i normally start the car? If so I haven't seen it, so I may have a bad bulb. One more thing to check.

SES light should display then go out like the other warning lights.

 

[CarolinaC4]

Since you don't currently have the FSM, see the article at Corvette Action Center | Tech | A Dose of Digital: Part 1 - The Basics - Page 1 of 5 for background info on OBD.

Next, I'd rule-out a bad ground at the DLC by conecting Pin B to a known-good chassis ground then turning on the key and seering if the MIL flashes.

If it doesn't you need the service manual's diagnosis information for a no-code-12 situation.

HI Hib,
I have read your article twice...good info. Is there a next part yet?
Should there be 4 volts at B with key on?

 

[vetteboy86]

With the ALDL connector untouched, no terminals shorted, nothing connected, when key is turned to on, not start, SES light should illuminate.

 

[Hib Halverson]

HI Hib,
I have read your article twice...good info. Is there a next part yet?
Should there be 4 volts at B with key on?

Part 2 is coming but not posted yet.

Several others have posted about bulb check. I forgot about that. When you turn the key on, you ought to see the MIL come on. Does it?