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Check engine Light flickering - HELP!

This is a discussion on Check engine Light flickering - HELP! within the Technical / Maintenance forums, part of the General Discussion category; Yesterday When I started my truck the check engine light was flashing fast (sort of flickering). I plugged in my ...

  1. #1
    "gadget" lowdown's Avatar
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    Check engine Light flickering - HELP!


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    Yesterday When I started my truck the check engine light was flashing fast (sort of flickering). I plugged in my diagnostic tester and the computer has no codes stored.

    The engine is idling fast (about 1500 RPM) and doesn't slow down when warmed up. It seems to run fine but there is obviously something wrong.

    I checked under the hood for loose wires or vacuum leaks and found nothing.

    Any ideas?

    Thanks in advance,

    lowdown

    1988 Chevy Silverado Stepside - 4/6 drop, Katzkin Leather
    Click on signature for truck pics and specs.
    http://www.koolcartoons.com

  2. #2
    Home of the Snooki punch! CKTA's Avatar
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    Re: Check engine Light flickering - HELP!

    IAC or TPS sensor?
    2014 Carlisle All Truck Nats info..
    http://www.fullsizechevy.com/forum/o...g-1st-3rd.html


  3. #3
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    Re: Check engine Light flickering - HELP!

    If the SES light is flashing fast and dim, that signals a failure of the PROM chip in the ECM or the ECM itself. Check connections at the ECM and make sure the PROM chip is firmly seated, if equipped.
    1991 K1500 - 'Red'
    350 Roller Cam TBI, 5-speed manual

    1995 Chevrolet Caprice 9C1 LT1
    Former Arkansas State Police

  4. #4
    "gadget" lowdown's Avatar
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    Re: Check engine Light flickering - HELP!

    Quote Originally Posted by cletus284
    If the SES light is flashing fast and dim, that signals a failure of the PROM chip in the ECM or the ECM itself. Check connections at the ECM and make sure the PROM chip is firmly seated, if equipped.
    That is what it is doing, I tested it again and this time I got it to thow a code...
    15 - "Coolant temperature sensor or circuit fault - signal voltage high"

    I'm going to go buy a new temp sensor and see if that fixes it.

    Thanks

    1988 Chevy Silverado Stepside - 4/6 drop, Katzkin Leather
    Click on signature for truck pics and specs.
    http://www.koolcartoons.com

  5. #5
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    Re: Check engine Light flickering - HELP!

    Double check that it is not a code 51 - PROM or MEM-CAL failure. This is consistent with your dim, flickering SES light. I'm getting this info out of my '91 Factory Service Manual.
    1991 K1500 - 'Red'
    350 Roller Cam TBI, 5-speed manual

    1995 Chevrolet Caprice 9C1 LT1
    Former Arkansas State Police

  6. #6
    "That'll buff right out."
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    Re: Check engine Light flickering - HELP!

    sounds like a short. check out that harness while your putting the temp sensor. let us know how it works out.
    2000 Silverado Z71 5.3
    1994 Blazer 5.7 TBI


  7. #7
    "gadget" lowdown's Avatar
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    Re: Check engine Light flickering - HELP!

    For those interested...

    First of all thanks to all for the suggestions, they really helped.

    It wasn't the Temp sensor, it was only 20 bucks so I started there - No Luck.

    I had an old Hyper-tech chip so I put it in and everything id fine now.

    lowdown

    1988 Chevy Silverado Stepside - 4/6 drop, Katzkin Leather
    Click on signature for truck pics and specs.
    http://www.koolcartoons.com

 

 

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