P0420 - Catalytic Control Efficiency Below Threshold

Discussion in 'General Motoring' started by Ron, Nov 23, 2008.

  1. Ron

    Ron Guest

    Hi, hoping for some advice. My daughters 1997 SC2 popped on it's check
    engine light this weekend. I went to Autozone for the code check and it
    came back with P0420 Catalytic Control Efficiency Below Threshold - Bank 1.
    Thoughts on what this really could be? I replaced the catalytic converter
    about 4 weeks ago and the front O2 sensor about 8 weeks ago. When we bought
    it 8 weeks ago, we were told the rear O2 sensor was replaced, no paperwork
    though. I had autozone reset the light and so far, it hasn't come back on
    with short in town driving.

    Ron, Nov 23, 2008
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