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  1. #1

    Question Weird O2 sensor readings

    Recently I bought an OBDII Bluetooth adapter to monitor my Tahoe's engine performance and see extra/more exact info from the ECU. Currently my o2 sensors are giving conflicting readings.

    What do I mean? Well the pre cat sensors at idle were reading a F/T of -1.6% for both the 1x1 and 2x1 sensors. While the post cat sensors are reading a F/T of 99.1% for both 1x2 and 2x2 sensors. Based on the info I've learned these readings are impossible. Does any one have an idea whats up with these readings? I have been getting a p0340 cat three way inefficiency code for the pass side cat recently, but the code keeps going away even tho its a major code that should stay in the ECU for a long time.

    Pic from torque app at idle:
    Click image for larger version. 

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    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage:

  2. #2


    the P0430 code indicates that you have an air leak on the passenger side, or the cat is bad, or that passenger side rear O2 sensor is not connected to the wiring harness, or the wiring is bent, broken, melted, burned, etc...

    what is the F/T reading supposed to be of?? it's not fuel trims, because the fuel trims don't go that high...

    2014 Camaro SS - 2SS, RS pkg., short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake

  3. Thanks Conlan Rose thanked for this post
  4. #3


    Is it possible that the reading from the rear sensors isn't actually fuel trim like the fronts and it wrong because they don't measure fuel they measure % of co2, co and o2.

    Also my p0430 code goes away on its own sometimes and only sporadically shows up. It makes trying to figure out what I need to fix very hard. Also the pass side used to have a weird sound for a while, which is now gone) I have a video of it I'll post and the pass side rear sensor is brand new (AC Delco)

  5. #4


    get a can of CRC Mass Airflow Sensor Cleaner from your auto parts store and spray clean your MAF sensor.... a dirty MAF sensor could be causing it as well....

  6. Thanks Conlan Rose thanked for this post

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