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obd2 codes throwing me off

Discussion in 'General Chevy & GM Tech Questions' started by greasemonkey, Feb 28, 2010.

  1. greasemonkey

    greasemonkey New Member

    i have three codes that are killing me one is catilyst below threshold bank 1 p420,catilyst below threshold bank 2 p430, and random multiple cylnder missfire p300 . I have checked all my o2 sensors they are all doing fine . I also have done a tune up on it plugs,wires,cap,button,on my 4.3 vortec and still am scratching my head so any help is greatly appreicated!
  2. unplugged

    unplugged New Member 1000 Posts

    What temp tstat are you running? The engine has to get warm enough to have the cat reach operating temp. Codes only give a clue and don't always point you in the right direction. I was just talking this morning about a friends pickup that was throwing cat codes and it turned out the 160 deg stat that works just fine in the summer wasn't getting the job done in the colder winter temps. In extremely cold weather I've even blocked the raditor with a piece of cardboard to bring the temps up.
  3. greasemonkey

    greasemonkey New Member

    the temp runs about 200 to210

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