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o2 sensor

  1. Knock Sensor and O2 Sensor Malfunction?

    Problems and Service
    Hello everyone, I need a little help here because I am very confused and need help picking a starting point. I have a 2008 cobalt ls, 2.2L 5 speed. I have had this car since 2008, it is my first car, she just turned 100k miles last year, and she is my baby! The last three years I have been...
  2. 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...