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I love my 09 TCH but, I just wish I understood the operation more. Maybe you smarter guys out there can enlighten me. In the following scenario, you are coasting, under 40mph, or at a stop, and your battery is not fully charged, (say 3 bars) the ICE is not off and is in fact running according to the rpm on my Scangauge and at the same time the MFD shows “no” arrows leaving the ICE, then what would be the reason for the ICE to be running? With these conditions wouldn't it make sense to be charging the battery?

Rick, what was the coolant temperature at the time? The engine may have been running to get the catalytic converter back up to operating temp.

Coolant temp was up to 185. Engine was up to operating temperature. I guess I could have reworded the question to be, why would the scanguage show the engine running while at the exact same time the MFD shows it as off?

Because the MFD doesn't actually show whether the engine is on or off -- just whether or not power is being used from the engine. This is how the Prius MFD works also and why you read occasionally that it was "lieing" -- it really isn't but may seem to if you don't realize that display only shows energy flow… not state.

Ok I think I'm getting it. The MFD pertaining to the ICE only shows energy flow not whether it is on or not. Some one else told me this once before but for whatever reason I forgot this information and was thinking when the arrows stop the engine was off which obviously is not the case. This explanation does help with my understanding on how this thing works. This whole thing may be simple stuff for some of you guys but for the rest of us it can be confusing at times. Thanks for the help. Rick

There are several conditions under which the ICE runs more,
arguably needlessly. Read the "five stages" document (http://techno-fandom.org/~hobbit/cars/five-stages.txt) for deeper
understanding [and note carefully that I did *not* write the
original, just added a couple of notes]. I believe all that
info about the Prius also applies to the TCH; we don't yet quite
know the exact criteria and thresholds for the gen-3 Prius but
it seems to have eliminated a couple of the more obvious bugs.
.
_H*

No problem, Rick -- we all understand that here and you'll find that we are as a whole quite patient with questions at any level. :)