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  1. #1

    Default P0171 p0174 issue

    i have a 2003 silverado 2500hd crew cab ls long bed 6.0l engine. At first i was getting p0101, p1133,p1153, p0171 p0174 until i changed out the fuel filter, the upstream 02 (before cat bank 1 and 2). There was hessitation and i would not want to idle. after changing those out, it idled fine between 650-700.

    I decided to change the MAF to get rid of the p0101 and it idles perfectly fine, drives fine but a few miles into it, i would get a p0171 code and p0174

    Things ive already changed, fuel cap, fuel filter, 2 O2 sensors, MAF sensor.
    Checked for vaccumm leaks with carb cleaners at intake manifold, intake pipe, no change in RPM

    I went to change the PCV but on my truck it doesnt have a hose, it has a plastic pipe that goes to a nipple on the valve cover.

    What could the problem be? do i need to take it to the dealer to reflash?

  2. #2
    Sr. Mechanic sc99z71's Avatar
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    I am having the same p0171 and p0174 codes on my 99 Silverado, except my CEL will come and go off at random. As of this morning it is off.

    I asked the dealer near about the intake manifold gaskets, and he said he didn't think that was the problem and he just doesn't see hardly any trucks in with that problem. He was kind of leaning towards the o2 sensors but you have already changed those out.

    One more thing, a buddy of mine has an 06 Silverado as a work truck and said he gets these codes randomly too. But they have a shop and he said that they have been all over this truck looking for vaccumm leaks and everything. Even checked all the sensors and all are working properly. The shop said there is absolutely nothing wrong with the truck and are thinking the computer is just wigging out.

    I would be interested if you get it reflashed to know if that fixes the problem. Also, does the dealership charge for something like that?
    99 Silverado 1500 Z71
    5.3L 4L60E Tranny
    TransGo Shift Kit
    2.5" Rough Country
    Suspension Lift
    33" BF Good A/T
    Cherry Bomb Turbo
    Cobra CB w/
    Dual Fiberglass Antennas

    01 Kawasaki KLR650

  3. #3

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    well it should cost 1 hr of diagnostic between 75-150. depending on the dealer. ima take it down to get a diagnostic or have them reflash it, whatever they say will fix it later on this week

  4. #4
    Sr. Mechanic sc99z71's Avatar
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    Let me know how that goes!

  5. #5

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    before heading to the dealer, i read the codes when i first started up and a different code p0300, i never caught this code before because i never read it when i first started it up. it would kinda idle slightly rough, not rough as in abnormal but if i were to try to pay attention to it, id notice, after it was warm , itll drop to 650-700 and stay smooth. i decided to do a search on google and this is what i came up with. even though i sprayed carb cleaner on the intake, its possible it could be hard to detect since its on the lower side of the manifold. im going to try to change the intake first, only $40. then if that doesnt fix it, off to the dealer i go.

    #PIP3232B: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum - (Feb 7, 2007)


    Subject: Cold Engine Idle Misfire or DTCs P0171 P0174


    Models: 2002-2005 Cadillac Escalade

    1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer

    1999-2005 GMC Savana, Sierra, Yukon

    2003-2005 Hummer H2




    --------------------------------------------------------------------------------

    This PI was superseded to update parts information. Please discard PIP3232A.


    --------------------------------------------------------------------------------

    The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

    Condition/Concern:
    99 through 05 GEN III truck engines may experience any of the following:

    A cold rough idle that diminishes as the engine warms up.
    Possible DTCS P0171, P0174, or P0300.
    Random misfires at idle.
    Recommendation/Instructions:
    The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

    If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
    The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
    Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

    GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

  6. #6
    Sr. Mechanic sc99z71's Avatar
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    I was afraid it was going to be the intake gaskets.

  7. #7

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    If I remember correctly, PO171 and 174 are bank one and two lean codes, I chased one of these not to long ago. Check fuel pressure, those are very picky, and the fuel pumps have a intermediate failure problems. It will not happen all of the time, but when it does, it will fall on its face. It will start out with a light hesitation, similar to a sticky throttle blade, then it will progress. I think those need 58psi to run, check it inside warmed up at idle, and ill bet its well under that pressure.

  8. #8

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    First of all with lean dtc's, and a generic misfire dtc. The p0101 will set due to leaking intake gaskets, the best thing to do is to check if the lean dtc's set at the same mileage because if it is a fuel pump they will set at the same time, if they set at different mileage most likely would lean towards intake gaskets. Stop throwing " parts til it starts", the money you spent the dealer would have fixed it right the first time.

  9. #9

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    100% intake gasket, took it off (intake bolts didnt seem to tight) and checked the head at the intake ports, seemed to have signs of leaking intake gaskets. Change the gaskets, and cleaned up the heads , and cleared up the codes. When to start it up and the slight vibration was gone, drop 100 miles and has never come back.

    verdict - intake gaskets

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