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> Training > 4-Wire Air-Fuel Sensor Diagnostics by John Thornton


4-Wire Air-Fuel Sensor Diagnostics by John Thornton

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Part 1 premieres on Tuesday February 7, 2023 CST, 7:00-9:00pm CST.
Part 2 premieres on Thursday February 9, 2023 CST, 7:00-9:00pm CST.

On the day of each live broadcast, Zoom will send you an email an hour before the broadcast begins.

One week after the live broadcast unlimited video access (24/7/365) will be available at the ASI website. Your login credentials for the ASI website will be emailed to you from AESwave. If you already have an ASI account use your existing login.


An important part of Air:Fuel sensor diagnostics is knowing how they function, which can lead to a simple and accurate fix. This class delivers the information every technician needs to understand how AF sensors work and a repeatable diagnostic routine for the DTCs they will encounter.

The class includes examples of Asian vehicle 4-wire Air:Fuel sensor issues with the goal to quickly prove whether the problem is caused by the sensor or something else such as a sensor issue, a feedback issue, or a wiring issue. John will explain how to perform a few multimeter tests to determine the cause.

Topic Covered:
- How 4 wire Air:Fuel Sensors work
- How to test them
- Specific examples of circuit testing for different OEMs
- How to perform quick checks with a multimeter
- Resolve conflicting data between AF sensor and rear O2
- Use fuel trim numbers to verify AF sensor performance
- Use scan data to verify operation

Instructor John Thornton

Class Length approx 4 hrs

PDF Class Manual included, to be downloaded after logging in to watch the video.

Streaming Delivery
Watch it live on the dates listed above; you will receive invite emails from Zoom.

On Demand Delivery
About a week after the livestream, watch the recording whenever you want at the ASI site! Login credentials for the ASI site will be emailed to you from AESwave.

About John Thornton
John discusses how to ground your scope during a seminarFor the past 20 years, John has provided the automotive aftermarket with hands-on and classroom training on a wide variety of topics, including: engine and transmission driveability, module programming, bus communication issues, and electrical diagnosis, lab scopes and scan tools. In the process he has become the foremost trainer in the nation for professional technicians, school instructors, and technical trainers.

The information and techniques John presents have been gleaned over 30 years in the Chicago area as a diagnostic technician, working in the bay and now as mobile tech. He is a mechanical engineer and has an extensive electronics background.

"If you go to just one class, ya'gotta go to John's class, no matter what the topic is."  Bob in IL.

"John is the trainer that other trainers are measured by." Harvey in BC.

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