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Check Engine Light - Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mstencel, Sep 6, 2002.

  1. mstencel

    mstencel Registered Member

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    Alright, here's one I haven't been able to figure out (without my mechanic's help, that is) My check engine light comes on, when I get my 1989 K5 on the freeway (Approx. 55+ mph). It comes on anywhere from 5 to 30 minutes of driving on the freeway, it always varies. It doesn't come on ever during city driving, it only happens on the freeway. If it comes on after freeway driving, and I stop and turn off the motor, the light is off when I restart. Any clues? It doesn't appear to affect the performance of my K5 in any way, but it sure is annoying. Any suggestions would be great. I thought it might be a cooling issue, but I've driven 4+ hours on the freeway, and the temp gauge stays at a constant 190. (Has brand new radiator)
     
  2. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    That's exactly what my 88 does. Anybody know??
     
  3. Calclips

    Calclips 1/2 ton status

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    A buddy of mine had a problem similar to this in his 89 heavy half ton pickup, and I believe that it turned out to be an O2 sensor that was bad. If your rig is TBI that might be something to look at.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    You getting an actual code?

    Have you changed tire size? Always was curious, if the tire size was off by a fair amount, and vehicle speed vs throttle position (both measured by computer) was different than the computer was "supposed to see" if that would trigger a code.
     
  5. Kyle89K5

    Kyle89K5 1/2 ton status

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    When my EGR initially went bad, that was pretty much the same sequence that it took for me to get the light. Not saying thats your problem, but you do need to check it out.

    You are getting a code. The easist way to check this out is to jumper the A & B terminals on the ALDL port under the dash with a paper clip. Do this with the key OFF, then turn the key to the run position but DO NOT START YOUR TRUCK!!! Count the series of flashes then go to your chiltons and/or your haynes book and see what the code is for. This is a start to diagnosing your problem.

    That light is coming on for a reason, ya might want to figure out what that reason is. When my EGR went south, the "percieved" performance didn't change, but the miliage went down and the truck started running pretty rich. Noticable on the back bumper where it waas now BLACK!!!
     
  6. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    I jumped the two terminals and I get a code 12. Also, I replaced the O2 sensor and EGR valve in March of 01. Is there somnething I need to replace or does code 12 mean its functioning properly?

    Thanks guys
     
  7. Kyle89K5

    Kyle89K5 1/2 ton status

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    IF that is the situation you are now in, then it's time to hook a scanner up to it. Look for a post called Code 42. I talk a little bit about a cheap scanner that I'm using now. It uses a software called WinALDL. It's not your average parts store "code reader" It's an honest to goodness scanner.
     
  8. Thunder

    Thunder 3/4 ton status

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    Sometimes (But not always) When the check engine light comes on but there no codes stored. it means the module in the distributor is going bad. it is one of the few problems that the computer does not store in its memory.
    I would try a new module.
    Code 12 means No distributor reference signal. it always shows when the Key is on and the engine is not running..
     
  9. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    Are there just replacement modules or performace modules and does anybody runnun them?
     
  10. Thunder

    Thunder 3/4 ton status

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    I'm using a performance module from these guys(link):Performancedistributors.com
    Scroll down the page and check out the 8 pin module.
    If you get one I would also recomend getting one of their screamin demon coils. Or A MSD Blaster 2 coil also works good they are a little cheaper.
    These gave me a nice little boost in low end torque. And my 350 will rev as high as i want it to without the ignition crapping out at high RPMs. like the stock stuff is prone to do.
     

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