Hi Steve - I have been noticing the same bi-polar behavior for the gear icon (Engine Drive Mode) when I have been on the highway lately. Sometimes it is sticky as glue and stays on no matter what, and other instances it is very stubborn about showing up at all. I had one 10 minute highway drive a few days ago where it came on for the first few miles and then would not return for the rest of it. I plotted the data below if anyone is interested. There were no other big changes happening during the drive - meaning the heat was not turned on, nor were any other electrical drains. The highway had some minor grades, but overall was fairly unremarkable. The grades during the first few miles were every bit as bad as the rest of the drive. Air temperature was 36F; dry conditions; HV-ECON mode.
In the chart, I plotted the ratio of RPM:speed (blue dots) to find the times where the Engine Drive mode is happening (36.0 - 36.7 RPM/mph; averages 36.35 RPM/mph) - those dots are re-colored orange in the chart. The brief instances around 3:46 and 8:08 were likely just a coincidence of engine speed and vehicle speed, as they only lasted a few seconds, and I didn't notice the icon on the display.
Just figured I'd pass it along as more OBD data to debate over.
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