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random check engine light with no codes...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jpaitala, Oct 28, 2003.

  1. jpaitala

    jpaitala Registered Member

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    I have a '89 K5 with 350TBI and manual trans.
    The problem is that I randomly get check engine light but no codes after the light. I previously had to change MAP-sensor, IAC-valve and O2-sensor. I had trouble codes back then and got rid of them by changing all these sensors.
    But now no codes... /forums/images/graemlins/confused.gif

    If I drive more than 20-30min a row, then most of the times I'll get check engine light, but not on shorter trips.

    What could this be?

    Thanks.
     
  2. mudjunkie 82

    mudjunkie 82 1 ton status GMOTM Winner

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    Sometimes during a situation where the motor is idling too low and is about to stall I have seen the check light flash and no codes
     
  3. 99firehawk

    99firehawk 1/2 ton status

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    Pull off your egr valve and make sure the that the egr port is clean, I have seen a plugged egr set a check light and not store the code. (darn! mazda)
     
  4. Thunder

    Thunder 3/4 ton status

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    Sounds like your Dist module may be going bad. When they go bad they will set a code 12.(No spark signal)Code 12 acually does not mean everything is OK. Like many people think. Code 12 comes up every time you check codes because the ign is on but engine is not running therefore not sending a spark signal to the ecm. The code 12 also indicates the ECMs Diagnostics are functioning.
    Dist modules, when they start going bad usually start giving troubles after they warm up.
    Lighting the CEL, missing, hard starting, stalling. with no codes(except 12) are symptons of a bad module.
     
  5. jpaitala

    jpaitala Registered Member

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    No stalling, no difficulties to start, no missing... Only check engine light. The egr could be it, I have not had time to check it, but I'll check it.

    Thanks for the reply's guys!
     
  6. 87BrnRsd

    87BrnRsd 1/2 ton status

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    Sometimes my check engine light will come on after I drive on the highway for a while. It is the egr valve. The computer just may not be storing that code properly.
    -Harrison
     
  7. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Agreed EGR.

    When you pull codes do you get code 12? You should see code 12 no matter what.

    -Dan
     
  8. jpaitala

    jpaitala Registered Member

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    Yes, code 12. So the "system" should be working...
     
  9. bpiccioni

    bpiccioni 1/2 ton status

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    I second the possibility of a distributor module problem.

    You might pull the distributor cap and make sure that the module still has thermal grease - perhaps it's getting too hot during your longer drives and giving you that code 12?
     

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