At idle and low rpm both O2 sensors were switching normally so I ruled out a vacuum leak being present. A fuel delivery problem would most likely affect both banks and I only had a code set for bank 2. I took a look at the freeze frame for the lean code. Freeze frame is a sort of snapshot of sensor data during the event that set the code.
Short fuel trim for bank 2 shows a LOT of fuel being added. It isn't likely I had a fuel delivery problem because bank1 looks to be in fine shape. I could also see this event was on a warm engine at highway speeds. I set up to monitor both O2 and went for a test drive. When I went from a steady cruise to a hard acceleration the bank 2 sensor went to full lean but bank 1 showed the increased fuel.
It was at this point I felt I was dealing with a bad sensor, bad wiring, or bad ecm. Easiest test from here would be replace the sensor and re-test. I did a wiring harness wiggle test while monitoring the signal and found nothing. Replacing the sensor and recording again under hard accel I could see I found the fix.
Not bad!
Thanks for reading.
Kenneth Hayes
G&G Auto Repair
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