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p0420
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  1. 11-16 LML Duramax Powertrain
    So this is driving me crazy; I had a shop here in California (yes, full smog check state) replace the 9th injector and a forced regen after a reacurring CEL for the P0420. Also had a oxygen sensor replaced just months before. So, no more light the the "permanent" code won't clear. No lights on...
  2. Introductions
    Howdy, new 6.6 2500HD owner from California, behind enemy lines! I'm anxious to learn what I can do to increase performance here in this state while remaining "legal" for the emissions sniffers, aka Tailpipe Nazis. I got my 2015 used about 6 months ago. It has 94k miles and just started...
  3. General Discussion
    I just hit 75k miles on my 2015 LML and just received a P0420 code. Code “P0420” - Catalyst System Efficiency below Threshold Bank 1. Can someone tell me this means that I need to change out catalytic converter or just the NOx sensor on Bank 1? Thank you for any help I can get on this. Rey
  4. 911 Problems Forum
    I instalked a mrbp 4 inch down pipe back last night with the stealth 2 quadzilla. I downloaded the update for the no dpf. I drove it to work today and now i have the cel light... So i checked it and tge code 0420 popped up. Should i drive it.... Will it limp? How do i fix this?
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