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o2 sensirs

  1. General Chevy & GM Tech Questions
    I've got a 2008 Avalanche LTZ w/5.3. I put headers on last week. It had 4 O2 sensors on it, the headers only had 2 O2 sensor ports, so I put the rear ones in and hooked them up. Now my check engine light is on. I can shut it off with my scanner. It comes back on within about 10 miles. Any ideas...