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  1. #1

    Default Lean on Banks 1 and 2

    yesterday i had the CEL come on. read lean on banks 1 and 2....this is the second time its came up. the first time i cleaned the MAF and disconnected the battery which was about a few weeks ago..and now its back. so im pretty sure it is not the MAF

    today the CEL went off and all i did to it was check the o2 sensors to see if they were bad. i have a feeling it is going to come back again...
    i am also experiencing less performance in acceleration from when i first bought the truck at 100k miles. it is a 2000 1500 silverado z71

  2. #2
    Jr. Apprentice
    Join Date
    Jan 2011


    Sounds like you may have a vacuum leak somewhere in your intake system. Check the lines real good. Replace your airfilter as well if you haven't already. Rick

  3. #3


    whats the best way to check for leaks? and is there a diagram on where all the vacuum lines are? one other thing...i have a CAI which i heard doesnt do anything to help performance... should i just take it off and see if that could help me also?

  4. #4


    a good way to test for vac leaks is to get some starting fluid or something of that sort and start spraying it around ur motor. if it revs up, u have a leak.

  5. #5


    if you have a kandn in the truck and its over oiled it will dirty the maf sensor within a couple days but i agree with the vaccume leak idea

  6. #6
    Jr. Apprentice
    Join Date
    Jan 2011


    I agree with badbrad, use some starter fluid. You should be able to pull up a good vacuum diagram from the internet. Your best bet is to first check all the intake vacuum hoses, and it's the cheapest way to start looking for problems. Once you get a good schematic diagram of your system, just trace all the hoses down and look for disconnections and holes, cracks, etc.
    I don't think that a CAI system would cause it to run lean, but it wouldn't hurt to put your stock air intake system back on and see if the service engine light stays off. If the CAI was causing it, more than likely it would have done it at the start of using it, when you first put it on. (unless something has come loose on it).

  7. #7


    another thing...even though my light went off. i can still put a scanner to it and it will read the same codes...that isnt normal is it?

  8. #8


    yeah its normal. the computer will store codes that caused the light to come on even if it goes back off. Also do you have an aftermarket MAF or is it stock. I had to take off the aftermarket MAF cuz it would give me the same lean codes.
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
    1960 Land Rover Series II 88
    2001 Pontiac Sunfire
    2013 Toyota Avalon Limited (Wife's Car)
    NRA Life Member

  9. #9


    i have the stock maf. and i took a plug out today. looks real lean. i also notice the engine stutter at idle, its not smooth like it should be.

    2000 1500 5.3 silverado with 106k miles

  10. #10


    if the light went off, does that mean im not running lean anymore? and should i change my plugs to AC delco irridiums?

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