In this video, I’m covering the methods I use to quickly identify lean conditions caused by dirty hot-wire MAF sensors, and what you can do to clean them. Hot-wire sensors are used by MANY different manufacturers, including Toyota, Mazda, Nissan, Subaru, Infiniti, Lexus, Mitsubishi, VW, BMW, Mercedes Benz and others.

Engine Performance Diagnostics chapter 12

symptoms 50

  • check engine light (P0171)
  • hesitation on acceleration

fix 50

  • clean the MAF sensor

test shown enh 50

  • using freeze frame data, live fuel trim data, to identify the type of lean condition
  • visually identifying a MAF sensor with an integrated IAT sensor
  • how to scope a MAF sensor signal
  • using the sensor ground during scope testing
  • analyzing a MAF sensor waveform
  • understanding how a dirty MAF sensor results in fuel trim changes
  • how to clean a MAF sensor, and which designs are able to be cleaned
  • understanding short and long term fuel trims countering each other after a repair

Tools used

  • scan tool
  • lab scope
  • brake cleaner
  • soft, small brush

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(Chapter 12) Mass Airflow Sensor Testing

Related videos:

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


How to troubleshoot a faulty MAF sensor (Mercedes Benz):


Dirty MAF Sensor Case Study:


MAF and lean codes from a missing air filter (P0171, P0174, P0102):


Low power, lean conditions (cracked air intake tube) GM:


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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!