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Thread: 3 failed flex fuel sensors? im lost

  1. #1
    Tuner in Training
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    Dec 2018
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    3 failed flex fuel sensors? im lost

    supercharged ls2 on 411 pcm with 2002 suburban flex fuel tune.

    My car was running great and then I put Granatelli coils on there and thats when it went down hill. Anyway my car started to run a little lean and I looked at my ethanol content sensor and it was reading 37.6%. I looked at my tune and that is the default percentage when the sensor fails. I bought a new sensor hooked it up and the sensor immediately read 100% ethanol. Then seconds later it slowly falls down to 37.6% ethanol again. At this point I reach my hand in the engine bay to mess with the sensor wires and I get shocked. Long story I got rid of the coils and put my original ones back on. So I assumed the coils were arching or something and fried the second sensor because they're somewhat close. Bought a third sensor and it did the same thing. 100% then slowly down to 37.6%. Ive checked wiring ground is good. Power wire shows 12v. Signal wire shows 5.07 volts. Any ideas

  2. #2
    Advanced Tuner jsllc's Avatar
    Join Date
    Sep 2015
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    Bozeman, MT
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    So I have run those coils for 3 years now. No issues. Not saying you did not or could not have a bad one but I do not believe they are the root cause of the issue. I have a sensor on mine as well. This is a wiring issue.

    In order to shock you, your body had to provide a better path ground path or it was holding the current imbalance. There had to be a built up charge that charge can either be yours or the cars. This is a imbalance in potential. Grounding issue?

    spark created with Gap between 60mm spheres
    volts
    0.5mm - 2850
    1mm - 4350
    2mm - 7350
    3mm - 10350
    4mm - 13350
    5mm - 16350
    Last edited by jsllc; 05-27-2020 at 11:11 PM.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  3. #3
    Tuner in Training
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    Dec 2018
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    Thanks for the reply. Ill check all my grounds. I must have moved something taking those coils on and off .

  4. #4
    Tuner in Training
    Join Date
    Dec 2018
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    A ground cable on the back of my drivers side head sheared off. This was probably the culprit of the shock. (tried to add a picture, i don't know if it went in or not). I don't know if this was causing the problem for the sensor yet.