OBD-I vs OBD-II
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Cadillac Seville / Cadillac Eldorado Forum Discussion, OBD-I vs OBD-II in Past Cadillac Vehicle Discussion; Hi folks. Check out this situation, and please let me know if any of you have some insights or advice... ...
  1. #1
    PalmFreightPete is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Jun 2009
    Posts
    14

    OBD-I vs OBD-II

    Hi folks. Check out this situation, and please let me know if any of you have some insights or advice...

    I just acquired a 94 Seville SLS. The original motor (Northstar) and transmission were swapped out in 2002; the replacements were from a wrecked vehicle with 30K miles. I don't know what model year the wreck was, nor do I know how to find out from the motor. But it delivered another 70K miles in this vehicle before I got it.

    Here's the challenge: The SES light is on and it's running pretty rough. So I thought I'd check the codes myself. I've got an OBD-II scanner, but this caddy has the OBD-I data link connector. So I used the ECC panel to check the self diagnostics, and... What the?!..... The PCM codes appear to have numeric values from the OBD-I table, but the format looks like OBD-II.

    I'm guessing now that the replacement motor was from a 1996, the year of transition from OBD-I to OBD-II. If so, how does that affect the troubleshooting process? And how do I go about getting replacement parts?

    Any thoughts or comments?

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
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    Jun 2004
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    Woodstock Ill.
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    Re: OBD-I vs OBD-II

    Is the silver cover on the engine just a non functional beauty cover or is it a bolted down functional part of the intake manifold?

  4. #3
    sven914 is offline Cadillac Owners Connoisseur
    Join Date
    Dec 2008
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    4,154

    Re: OBD-I vs OBD-II

    The ECC might have been removed from the computer controlled system, or does not have diagnostic abilities.

    To diagnose the car using the OBD-I ALDL, look at the connector for a raised notch. The raised notch is considered the top of the connector. If the notch is on the physical top of the connector, insert a paper clip into the last two holes of the top row. If the notch is on the physical bottom, then insert the paper clip into the first two holes of the of the bottom row.

    With the paper clip in place, turn the ignition to the run position, but DO NOT start the engine. The check engine light should begin to flash. Count the number of flashes. They will count out two digit codes. The first one will be twelve and it will count as follows: 1 flash/pause/2 flashes. Follow this link to decipher the codes.

  5. #4
    PalmFreightPete is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Jun 2009
    Posts
    14

    Re: OBD-I vs OBD-II

    It's bolted down. And there are 4 holes in the top it, through which I can see the bolts for the intake manifold. My manual has a picture of the "manifold service cover" on 95 and later models. That one has only two nuts holding it down. I'm guessing that's what you mean by a "non functional beauty cover"? So mine must be functional, eh?

  6. #5
    PalmFreightPete is offline Cadillac Owners Member
    Automobile(s): 1994 Seville SLS
    Join Date
    Jun 2009
    Posts
    14

    Re: OBD-I vs OBD-II

    Hey Ranger, was that question about the manifold cover a quick way to determine when the engine was made?

    And Sven914, I've used that paperclip technique before (on other cars) and I'll keep it in mind. Meanwhile, I'm pretty sure the ECC panel is connected to the computer controlled system, and is functional for diagnostics. It even reported a new code when I checked it again a day later. When I go through the menu options it'll show PCM inputs, outputs and data values. Cool stuff, if I new how to interpret them. I've now reset all the codes, and will wait to see what happens next.

    I just don't understand how an OBD-I system can report codes in the OBD-II system format.

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    70,351

    Re: OBD-I vs OBD-II

    Hey Ranger, was that question about the manifold cover a quick way to determine when the engine was made?
    Yes. Only the '93 & '94 used that manifold.

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