Mazda MYSTERY No One Could Solve - Part 1 (P219B - Bank 2 Air-Fuel Imbalance)

I have a feeling this one won t be easy... This 2015 Mazda CX9 has a persistent Check Engine Light at 80k miles. Dealer already performed a SKETCHY "harness repair" which involved chopping off and re-routing the harness for the Bank 2 Air Fuel Ratio Sensor... Amazing haha xD Code set: P219B - Bank 2 Air-Fuel Ratio IMBALANCE. What does that mean?? Let s start from scratch, collect some data, and come up with a game plan on what exactly to test on this Mystery Mazda. How would YOU diagnose this car? THINKTOOL PROS: https://www.amazon.com/dp/B08XXWHQVJ?tag=onamzpineholl-20&linkCode=ssc&creativeASIN=B08XXWHQVJ&asc_item-id=amzn1.ideas.NHZL00NIDEPF Enjoy! Ivan