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Need help please!

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by johnlazelle, Oct 6, 2013.

  1. johnlazelle

    johnlazelle New Member

    I have a 2002 GMC Yukon XL 1500 5.3L flex fuel model with 150,000 miles.

    It runs rough at an idle and cuts in and out going down the road, especially uphills, but smooths out some when i really seem to get after it and kick it down a gear or two.

    I borrowed a code reader and got the following codes:

    P1639 - 5-VOLT REFERENCE B CIRCUIT FAULT
    P0300 - MULTIPLE CYLINDER MISFIRE
    P0332 - KNOCK SENSOR CIRCUIT LOW BANK 2
    P0452 - EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE SENSOR LOW INPUT

    I have done the following:

    replaced spark plugs
    replaced fuel filter
    replaced fuel pressure regulator
    replaced intake manifold gaskets
    added fuel injector cleaner (twice) to gas
    replaced passenger side upstream O2 sensor

    After i replaced the fuel filter, a friend let me borrow a fuel pressure gauge and we were getting about 45 psi. I have not checked it since i replaced the fuel pressure regulator.

    It feels like its starving for fuel.

    Some suggestions i have gotten are as follows:

    Check catalytic converters
    possible injector problem?
    O2 sensors?
    Fuel pump?

    Would the knock sensor code cause the engine to run rough and misfire??

    Please, any advice, suggestions or recommendations appreciated.

    John

  2. rileyjr16

    rileyjr16 Rockstar 3 Years 1000 Posts

    Mine threw knock sensor codes for both sensors but as far as I could tell she didn't seem to run that bad. She had a good octane knock going uphill and towing something but my truck never misfired when they were bad. I would definitely look into replacing the knock sensors though. Also could be everything you said.

    Another member on here has the same vehicle and much more knowledge than I have on those trucks.
    [MENTION=51590]Pikey[/MENTION] is his name. Maybe he'll see my tag and come to the rescue
  3. johnlazelle

    johnlazelle New Member

    Thanks. My friend who is a mechanic worked with me today and ruled out the cats and o2 sensors, he's leaning towards the fuel pump.
  4. RayVoy

    RayVoy Active Member 2 Years 1000 Posts

    I know that pressure is low for the next gen of trucks, not sure what pressure your truck needs.

    A search on this site should find the recommended pressure.
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Maybe somebody that knows for sure will be able to validate it but I think the fuel pressure is low, I thought it should be about 10psi higher.
  6. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    So, give us an update. In our last PM I recommended checking and cleaning the pcm connections. You said that you disconnected it and reconnected (therefor cleaning corrosion off the pin) and the problem was solved. Is it still fixed??
  7. johnlazelle

    johnlazelle New Member

    Still fixed! It's been over a week and not one problem has been experienced! Thanks again for your help.

    John
  8. ChevyFan

    ChevyFan Administrator Staff Member 5+ Years 5000 Posts

    That's great news.
  9. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    Wooohooo! +1 for the good guys! I did tons of research for that one. I had to use a friends shop address and phone number and pretend I owned a shop to get access to a auto shop only website where I thought the answer might be. A shop owner there had the exact same codes and found a broken wire running to the pcm. Happy to hear that it is good.

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