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  1. #1
    Sr. Apprentice
    Join Date
    Nov 2009
    Location
    south jersey
    Posts
    36

    Default system to lean bank 1 and 2 codes what should i do

    Ok guys so yesterday comming home from work my engine light came on and instantly my truck started to run rough and my trans began to slip terrably. I put it on the comp and 2 codes came up "system to lean bank one" and "system to lean bank two" I replaced the throttle positioning senSor and cleaned my mass air sensor and it did nothing for me. next would b the 02 sensor and fuel filter but with the o2 sensor should I change the upstream or down stream? Any help would b appriciated thanks guys
    99 4x4
    slp exh. 20s
    blacked out
    goodmark cowl hood

  2. #2

    Default

    it'd be the first O2 sensors, before the cat... those are the ones that are used by the ecm to determine the fuel trims...

    the rear O2 sensors after the cats are just used to determine if the cats are working properly...
    06MonteSS


    2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake

  3. #3

    Default

    i dont know if this might help or not, but a buddies sport trac from work gave the same type of codes and his maf ended up needing to be replaced

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