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Thread: O2 sensors...UGHHHHHHH

  1. #1
    Join Date
    Jul 2014
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    Houston
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    O2 sensors...UGHHHHHHH

    I'll make this brief. Did LS 4.8 swap, engine, trans, harness and all as unit from donor vehicle Into my 91 Silverado. Replaced harness with a unit from affordable efi and had the PCM flashed three different times to ensure it was working (twice by affordable and once by Brandon at LT1 swap). O2 sensors will not switch (move between .450 and .460 mv) truck runs very rich but idles ok. Fuel maps not registering. I have checked the wires going to the front passenger O2 sensor both with the truck running and ignition on engine off. I get 12v for the signal, I have a 12v ground and the heater circuits read .3-4 mv. I have used so many different types of O2 sensors I should go into the business of selling them. I have tried both case and isolate styles with no luck. The plug on the truck harness is square. I have used square and flat O2's (using a harness from square to flat). Any insight would be GREATLY APPRECIATED.

  2. #2
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    Jul 2014
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    Any help guys? Just looking for a little input.
    Thank you as always.

  3. #3
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    SAN ANTONE
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    i would double check the pin out on the harness to be sure that is correct.
    06 rcsb, 6two, 231/235, 4.11, pacesetter, 80e, 14 bolt, Nelson tuned
    2011 rcsb 6two swap in the works with 6l90 and boost
    FARMTRUC CAN GARGLE PEANUT BUTTER

  4. #4
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    I checked it some time back but will look again.
    Thank you

  5. #5
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    what year is the harness built for
    06 rcsb, 6two, 231/235, 4.11, pacesetter, 80e, 14 bolt, Nelson tuned
    2011 rcsb 6two swap in the works with 6l90 and boost
    FARMTRUC CAN GARGLE PEANUT BUTTER

  6. #6
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    Quote Originally Posted by Ray@NP View Post
    what year is the harness built for
    The harness was built for a 2002 Silverado. I provided the PCM from the donor 02 Silverado (I got the engine ,transmission, PCM and complete factory harness at one time) the company for a reflash. When completed the company sent me a video of my PCM and the new harness running their engine. The VATS was removed, rear O2's, EGR, the usual stuff. The engine fires right up but O2's just won't respond.

  7. #7
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    Jul 2014
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    I am wondering, since I have no experience with them, would a wide band O2 sensor help with this problem. Just grasping as straws.

  8. #8
    Join Date
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    Location
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    how are you checking your readings? with a meter or scanner or both? also you stated the voltage should move "(move between .450 and .460 mv)". pretty sure its between 0 and 1ish. either way you should get fluctuation on the front o2's all the time. are you positive the front o2's arent disabled? if your using software what, are you using? you say you checked the wires. you mean you physicallly traced them to the correct pins on the pcm? if its flashed correctly it sounds like a wiring issue especially since you said you replaced the sensors multiple times. i would confirm wiring for sure even if you have to make your own temporary harness.
    Like Tumbler in "Gone in 60" I'll drive anything with wheels or without

    My 95 ECSB LQ9 build thread - http://www.ls1truck.com/forums/lsx-t...to-95-obs.html
    CALI LEGAL ENGINE SWAP!
    Stock 03 LQ9, DBW, 95' 4l80e w/ Transgo shift kit, 2010 50# GM injectors, 2800 Circle D stall, Spectre CAI, Upgraded trans cooler, Home-made E-fans/shroud, Dual EP-381 fuel pumps w/Home-made hotwire kit
    NEXT ON LIST: Dual Battery setup, CAM/Valvetrain upgrade, Build my own rear mount turbo, TRU-TRAC, HIT THE STRIP!!!

  9. #9
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    I am checking the readings using both a scan tool and volt meter. The scan tool indicates little to no activity I the O2 sensors in mv and no fuel maps. The volt meter indicates a good +12v, 12v ground and between .3-.4 mv (engine running). The front O2 sensors are not disabled. I believe this because the PCM has been checked three times (twice by affordable fuel injection and once by Brendan at LT1 swaps). Here is what I found today...I checked for continuity in all four wires on the O2 sensors plugs on the harness. The driver side checked out as follows; black had continuity and was located in pin 1, pink had continuity and was located in pin 3, tan/wht had continuity and located in pin 29, and ppl/wht had continuity and located in pin 69. Now for the passenger side; black had continuity and located in pin 1, tan had continuity and was located in pin 26, ppl had continuity and was located in pin 66, no matter what pink wire i tried in blue or red connector, the Pink on the passenger side HAD NO CONTINUITY! What I find mind boggling about that is when the truck is not running with ignition on I get 12v, and with the truck running I get 12v, how is this if there is no continuity. Sorry for the long post. I really appreciate the responses.

  10. #10
    Join Date
    Mar 2013
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    pink is usually hot power. havnt checked diagrams but i think the pinks are going to a always hot fuse. pcm controls the ground to make the circut.
    Like Tumbler in "Gone in 60" I'll drive anything with wheels or without

    My 95 ECSB LQ9 build thread - http://www.ls1truck.com/forums/lsx-t...to-95-obs.html
    CALI LEGAL ENGINE SWAP!
    Stock 03 LQ9, DBW, 95' 4l80e w/ Transgo shift kit, 2010 50# GM injectors, 2800 Circle D stall, Spectre CAI, Upgraded trans cooler, Home-made E-fans/shroud, Dual EP-381 fuel pumps w/Home-made hotwire kit
    NEXT ON LIST: Dual Battery setup, CAM/Valvetrain upgrade, Build my own rear mount turbo, TRU-TRAC, HIT THE STRIP!!!

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