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low cat threashold

  1. P0420-After Complete Exhaust Replacement

    Problems and Service
    A few months ago, my car threw the TC P0420. I didn't have the money to deal with it then, but over the last 6 weeks, I've been trying everything I can to no avail. First, I took it to the shop. They charged me 400 for an upstream sensor. CEL came back on. Then, they said I had to replace the...