Here’s part II of my wideband O2 case study. I cover some further voltage and current testing on this vehicle and go deeper into the operation of this type of wideband sensor. While we found that the low amp probe won’t work in this application, we did find that some of our ‘normal’ zirconia O2 sensor tests carry over, and are still effective during diagnostics. I also got to review some fuel trim analysis and MAF cleaning as a final fix on this vehicle.

Engine Performance Diagnostics chapter 5

symptoms 50

  • pending trouble codes (P0171, P1130)
  • intermittent rough idle

fix 50

  • replaced the bank one upstream wideband O2 sensor
  • cleaned the MAF sensor

test shown enh 50

  • using scan data to evaluate wideband O2 performance
  • how to test for a wideband O2 sensor problem or an actual lean condition
  • using the Snap-On Troubleshooter during diagnostics
  • understanding Toyota wideband O2 voltage operating ranges and circuit design
  • scope testing a wideband O2 sensor
  • understanding Toyota processed wideband O2 sensor data compared to voltage readings

Tools used

  • scan tool
  • lab scope
  • propane

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(Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing

Related videos:

Wideband O2 sensor testing, P1130 (Lexus RX-300) - Part I:


How to identify and clean a dirty MAF sensor (Subaru):


STFT reads opposite of LTFT (after repair fuel trim data):


2014 Subaru WRX O2 Heater Test (P0037, P0141):


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!