Engine Service Soon light on but no codes??? 94 Concours
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Northstar Engines and System Technical Discussion Discussion, Engine Service Soon light on but no codes??? 94 Concours in Cadillac Engine Technical Discussion; My 94' Concours has the Engine Service Soon light on. After starting the car it sometimes stays off for a ...
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    Engine Service Soon light on but no codes??? 94 Concours

    My 94' Concours has the Engine Service Soon light on. After starting the car it sometimes stays off for a few minutes and then comes on. They it stays on the entire time. I ran the codes and nothing current at all. Any ideas? Wouldn't it show up in the codes or do you have to count the engine service light flashes on these cars too? Any info would be appreciated.
    I noticed my gas mileage isn't very good. It is around 14.2-14.9mpg. I am not sure if that helps in anyway. Thanks.

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    To the best of my knowledge, if the SES light illuminates there has to be a code stored.

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    I think the SES light is comes on when you have emission problems, for the most part. Fuel milage might be o2 sensor or something like that, it should have a code since it lite the light. If you turned the car off, its no longer a current code.. Clear the codes.. go drive it around, pull into a parking lot with the engine still running and check the codes. Although they might not be current.. which mean its intermittent, and that it has corrected itself when it was last tested. It's still a problem

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    Believe it or not I just cleared the codes and drove it around and it still came on.
    I tried again and again and it still came up all monitored systems ok.
    Every time I ran the codes it said no---, no---.
    I went ahead and went into the PCM Data and checked my 02 sensors. The front was .11 but jumped to .71 for a second. The rear one was .17 and then jumped like the front one to .91. Is this normal? Thanks.

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    Something odd here....if the service engine soon light is on there has to be a code.

    You can check the codes with the engine still running when the light comes on. Watch the DIC carefully as possibly the code is being missed in the process of entering the onboard diagnostics.

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    Ok, I will try it again today. I thought for sure there would be a code also. Well, it must be there so I will keep checking until it comes up. Thanks Again for all of the info. I will keep you posted.

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    Quote Originally Posted by Twilightcall
    Believe it or not I just cleared the codes and drove it around and it still came on.
    I tried again and again and it still came up all monitored systems ok.
    Every time I ran the codes it said no---, no---.
    I went ahead and went into the PCM Data and checked my 02 sensors.
    I'm confused... you mention "all monitored systems ok". That message is not part of the diagnostics. It is part of a normal display (not a diagnostic display). But since you do know how to check the PCM Data, then I assume that you know how to get into the diagnostic mode.

    Have you tried to go into the diag. mode while the light is lit ? Then when the display of all the diags completes (without any codes stored) have you exited the diagonstics (without clearing anything) and the light was still lit ? This should not be possible.

    Also, there is a way to trigger a "snapshot" of the PCM by hitting some combination of buttons (while not in the diag mode). That might be helpful in troubleshooting this. But I don't recall what keys to hold down to trigger a snapshot (it is mentioned in the Service Manual).

    Peteski

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    Re: Engine Service Soon light on but no codes??? 94 Concours

    i think customer snapshot for that model is to hold 'Off' and the 'Front Defogger' button for a few seconds.. the SES light should flash and you can access the data .. it will be labeled 'snapshot001' or something like that.. it also takes a snapshot when a code sets.. so maybe you can scroll threw those and see. those are stored as 'snapshotXXXX' where XXXX is the code.

    Your right, it should still have the code or set a 'memory loss' code.
    only other thing i can think of is a a faulty IPC. weird

    ohh yeah, for the 02 sensor.. thats actually a voltage. its gonna vary when you check it.. what happens is, it warms up as the engine does. like 15 minutes of driving is when you want to check it. i'll check the value against my 93 Northstar.. should be about the same? it's all i know

    and dont forget... those history codes are important too!

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