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  1. #1
    Sr. Apprentice
    Join Date
    Jan 2011
    Coeur d'Alene, Idaho, United States

    Default Service Engine soon light

    I have been having an issue with the Service Engine Soon light coming on completely randomly on my 91 K1500. It only happens at highway speed but with no rhyme or reason. I will be traveling at highway speed and it will come on, then with no change in speed or terrain it will go off. Anywhere from 15 to 45 minutes on then anywhere from 15 minutes to an hour later it will come back on. I have recently had the oil changed, tranny checked (OK per tranny shop) and it has a fresh tune up in December. Nothing changes in the way the truck acts when the light is on or off. Is this something to be concerned about? I know that it says service engine soon so it isn't like a warning to get the thing off the road right now but it makes me nervous to have any dash light on. It would make more sense to me if it came on and stayed on but this intermittent deal is making me really nervous.
    1991 Chevy Suburban, 190K, 1500 1/2 ton, 5.7L, 3:42 gears, 4X4, stock tire size, stock suspension set up.

  2. #2


    Have it scanned for a code. Find a shop that has a scanner that can scan engine and transmission.

  3. #3


    x2 silveradotrailblazer.....

    if you were near by i'd lend you my code reader. yes, they are worth owning and don't cost that much. reader help isolate the issue and pay for themselves quickly. good luck.

  4. #4
    Jr. Apprentice SkullMountainRider's Avatar
    Join Date
    Mar 2011
    British Columbia, Canada


    Most of the time it will be the Oxygen sensor or sensor in general. I've got the same problem with my 90 and that's what I've figured. It still runs like a clock though.

  5. #5
    Sr. Apprentice
    Join Date
    Jan 2011
    Coeur d'Alene, Idaho, United States


    That's what gets me SkullMountain, it continues to run exactly the same as far as I can tell. If it doesn't change anything why is the darn thing there? Just to make people like me nervous? Oh well, I found a friend that has a code reader that works for my year and I can hopefully meet up with him this weekend to see exactly what it is.

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