Oxygen Sensor O2 Readings.

Posted in Ignition Systems
  • I only used one autoXray to scan my 1995 GMC Sierra. 350TBI. The O2 sensor readings went up and down, which I understand is normal. My question is, it is normal to go from 100mV 850mv up and down again and again. Are these numbers within a acceptaboe area and is “consistent” normal fluctuation. All other sensor readings appear normal and the truck is not sending any codes. I just stutter the hunt for a miss / for a while now. Connector, cable, cap, rotor and ignition coil have been been changed as part of a tuneup in the week. The throttlebody been cleaned. Please help.

    There are 2 Answers for "Oxygen Sensor O2 Readings."

    1. happy2b_white says:

      There’s an issue in the fuel injection system, a bad sensor somewhere would be my guess. Have it scanned by a professional.

    2. Chris says:

      A fluctuating O2 reading is a sure sign they should be changed. If your OBD2 then you may have two 02 sensors. Get those replaced and see how it changes the running status. If you still have the miss, then it can be a few things I have encountered: ignition module, bad injector, and fuel pump. You have done the other things I would have done. I have been chasing a miss on my 01 Malibu for a year now. Found out that I had two bad spark plug crimps on the wires and it runs sweet now. Good luck.

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