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Thread: l5p trouble tuning

  1. #1
    Potential Tuner
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    Aug 2023
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    l5p trouble tuning

    I got the HP tuner with the unlocking device on my 2020 2500 chevy. hooked everything up and started downloading the 2 tune files i was sent. for some reason now the truck is telling me to change air filter and my engine is reduced power. it doesnt sound like its idling right at all. any help at all would be great thanks!!

  2. #2
    If its in reduced power...did you take off any emissions? If so sounds like your tune doesn't support such modification.
    2006 GTO 403ci lsa heads kooks long tubes corsa ss exhaust OTR intake HPTuned

    2010 GMC Sierra LMM Duramax. Exhaust and tuned

  3. #3
    Potential Tuner
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    Aug 2023
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    Yes it’s now straight piped and it’s supposed to be a tune to support that

  4. #4
    Potential Tuner
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    Aug 2023
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    so the issue was probably i didnt have my can bus plug kit installed. i feel stupid for even asking this but where is the location of the plugs the kit has to be plugged into

  5. #5
    From Google search (and learned something myself since i'm not familiar with tuning an L5P): "L5P Plugs will replace the nox and def module when the exhaust/def is removed from the L5P for racing. They will keep the CAN-BUS alive to the fuel tank and maintain normal ECU operation for fuel tank/lift pump data. These plugs can be utilized or the factory modules left plugged into the harness and zip tied up." SO Id expect the plugs to be underneath near these sensors.
    2006 GTO 403ci lsa heads kooks long tubes corsa ss exhaust OTR intake HPTuned

    2010 GMC Sierra LMM Duramax. Exhaust and tuned

  6. #6
    Tuner in Training
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    Jun 2023
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    The big tan one is for the def module connector (located directly above def tank I believe, under truck). Takes a second but you’ll fine only one like it on top of a tank. The other (4 or 5 I think) black ones , plug in to connectors along the exhaust for nox sensors and there’s one under the hood I believe that plugs into the nox sensor that goes to the CAT mounted on the back of the turbo just before the down pipe. I did mine awhile ago , took me some research and even got ahold of the can plug manufacturer to find the def one. Managed to find them all.
    Also word of advice, the differential pressure sensor (one with tube going to it led from BEFORE the DPF, and one tube going to it that’s tied in AFTER the DPF, you can’t unplug this sensor it or idles weird , need to leave it plugged in and just loop the two tubes together to create a “open-air” situation to the ecu.
    2019 Silverado 2500 High Country Duramax
    2008 6.4 Powerstroke

  7. #7
    Tuner in Training
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    Jun 2023
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    And there is one extra plug that my kit didn’t come with a plug for , all the way back on the exhaust I believe. Pretty sure it’s an o2 sensor , but it definitely reads exh temp because it runs fine when I unplug it, but only negative side ive seen is that when I run diagnostics, I can’t get a back exhaust temp reading unless it’s plugged in.
    Just my $.02
    2019 Silverado 2500 High Country Duramax
    2008 6.4 Powerstroke