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Thread: 2011 silverado 5.3 o2s randomly quit

  1. #1
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    2011 silverado 5.3 o2s randomly quit

    I'm working on a all stock Silverado that all the o2s will randomly quit reading, and the truck will start chugging bad. if I keep the rpm above 2,000 they will start to read but once I let off they go dead again. sometimes if I tap the throttle I can get them to come back alive and read again. they are brand new gm o2 sensors all 4 and I ordered a new pcm and flashed it thinking the driver inside was bad but the new one does the same thing. ill post the log see if i'm missing something or give some guidance on what else to check cause right now i'm scratching my head.


    thanks in advance
    Attached Files Attached Files

  2. #2
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    what codes do you have?

    I havent looked at your log file yet but those trucks in stock form have wiring harness issues. The wiring can get rubbed trough, or even a break in a wire. sometimes they rub on the frame or driveshaft. inspect all the wiring for the O2 sensors.

  3. #3
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    I've triple checked the entire harness. that was my first thought when this came in acting up. im getting p0171 and p0174 banks 1 & 2 fuel trim lean when it starts acting up. when this happens my long term and short term fuel trims peg to 29.5 I've checked for vacuum leaks and has none. it's gotta be a wiring issue or something is back feeding and taking 02s out.

  4. #4
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    So I just looked at your log file. One thing that stands out is your MAF readings. when it acts up, and your O2 readings are under 50mv the MAF has dropped into the 3-4 g/s range but your still idling above 600rpm, thats not really possible with a 5.3l engine. Your either have a vacuum leak, or your MAF sensor is dirty or bad and is under reporting the actual air flow. double check for vacuum leaks, the PCV hose can crack and cause this problem, also the push connect fitting for the brake booster hose, or intake gaskets. Remove the MAF sensor and see if its dirty. You could try and clean it, or swap it out with another one. If this truck as a K&N style air filter it can cause this problem.

  5. #5
    Senior Tuner 10_SS's Avatar
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    I just looked at your log. They do not stop reading, they work fine. They are just showing a lean condition is all. Your engine is running like crap because it's lean there? Or do you think it's actually running rich when the 02's say lean? You would need to confirm that. I think a missfire could do that also.

    Your LTFT are showing it's trying to add 29% fuel, so you have something else going on like WAK said, maybe a vacuum leak if everything is stock.

    It is strange though it looks like it's running fine at 600rpm with 2% fuel correction then you rev it twice then it says it leans out, then it starts adding the 29% fuel.
    Last edited by 10_SS; 3 Weeks Ago at 10:24 AM.
    2010 Camaro LS3 (E38 ECU)
    Whipple 2.9L, 3.875" Pulley, kit injectors, supplied MSD Boost-A-Pump, stock pump
    LG Motorsports 1 7/8" Headers - No Cats, stock mid pipe with JBA Axle Back
    ZL1 Wheels/Tires

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    has a new MAF in it, but at this point ill try anything. ill have a new one sent and try it.

  7. #7
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    its very strange because for most the day it drove fine then started doing it's weird thing again. it has all new plugs and wires in it and i even took a known set of coils just to be safe because it did have random missfires at idle. now the only time it starts to missfire is when it shows the lean condition and starts trying to add fuel. also i went back through to check for vacuum leak with brake clean and found nothing

  8. #8
    Senior Tuner 10_SS's Avatar
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    Quote Originally Posted by dfost33 View Post
    has a new MAF in it, but at this point ill try anything. ill have a new one sent and try it.
    tune the MAF out, see how it runs SD.

    The way it switches to lean like that I dont think is a standard vacuum leak, it's almost like it's a valve opening up.. is that possible? Solenoid, evap? Large leak.

    Who knows, are the injectors and data correct?
    2010 Camaro LS3 (E38 ECU)
    Whipple 2.9L, 3.875" Pulley, kit injectors, supplied MSD Boost-A-Pump, stock pump
    LG Motorsports 1 7/8" Headers - No Cats, stock mid pipe with JBA Axle Back
    ZL1 Wheels/Tires