GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 3 of 3
  1. #1
    Sr. Apprentice
    Join Date
    Nov 2009
    south jersey

    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


    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...

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

  3. #3


    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

Similar Threads

  1. Bank 1 to lean, trouble code, help
    By itsabowtime2 in forum GM Powertrain
    Replies: 29
    Last: 03-19-2010, 11:16 AM
  2. Hoe running to lean???
    By Bobby1021 in forum General Chevy & GM Tech Questions
    Replies: 1
    Last: 01-04-2010, 10:01 PM
  3. System too lean???
    By philosofy1 in forum General Chevy & GM Tech Questions
    Replies: 0
    Last: 12-08-2009, 10:04 AM
  4. P00174 Bank 2 Running too lean
    By Schwindle in forum Performance & Fuel
    Replies: 2
    Last: 08-13-2009, 05:43 PM
  5. lean codes P0171 + P0300
    By edsz71 in forum General Chevy & GM Tech Questions
    Replies: 8
    Last: 03-18-2009, 07:38 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts