In this first part of a two-part series, I get my hands dirty on a 2000 Lexus RX-300 with a wideband O2 sensor problem. As I show in the video, the operation of this sensor is very different to a ‘normal’ O2 sensor, and requires some different testing methods. Check out Part II for the conclusion.

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 II:


How to identify a bad oxygen sensor (signal fixed rich):


O2 sensor testing (fixed lean) P0174, P0154, P0155 - Mitsubishi:


Understanding Short Term and Long Term Fuel Trim (an SD Premium video):


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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.

Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium. There is a 14 day free trial.

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!