Engine still running in park?

Nothing I've ever seen.

 

sounds normal to me. unless gen 4 develops the gen3 detonation at start up, i think you can shut it down anytime.

 

Yep - it does it. No problem - just turn it off. It'll work it out, it's computer knows more about what it's doing than we'll ever know. It's probably got thousands of pages of code we'll never figure out.

Keep the "ENERGY MONITOR" and it'll give you a better idea of what's going on than the Hybrid System Monitor:

 

Not doubting you but why? I've just been stopping and shutting mine off for 11+ years. For better or worse, I trust Toyota to have programmed the vehicle to operate as it should.

This is where a Scanguage or Hybrid Assistant app with OBDII adapter will tell you for sure what the ICE is doing. Probably depend on state of charge, temperature, etc.

 

No. In the Owner’s Manual (PDF), the energy monitor features of the multi-information display (pages 125–126) and 7-inch audio system screen (pages 162–166) are described as showing energy flow, not the status of the engine, for which there is no driver-visible indicator.

Unless there are warning lights or a stored diagnostic trouble code, I wouldn’t be concerned that the engine also runs for purposes other than propulsion or HV battery charging, such as to maintain a warm temperature in the cabin.

If you’re really concerned, I suppose you could use a Toyota Techstream diagnostic system—or a third-party diagnostic tool, as @royrose kindly suggests—to check these Data List items, under Hybrid Control:

• Engine Idling Request
• Engine Start Request (A/C)
• Engine Start Request (Engine Warm-up)
• Engine Start Request (Hybrid/EV Battery Charging)
• Engine Mode

See the Repair Manual (more info) for details.

 

What screen?

 

This was a thing for Gen3 engines that had just fired up on a stone-cold start. I'm not remembering it applying to any warmed engine conditions.

 

The energy monitor?

 

Does the screen REALLY show "nothing running" or just that no energy transfer is taking place ?
I think it might be perfectly normal for the engine to run for a short time to do some "house keeping" without generating any power.

 

If the engine is cold, it'll want to finish its warmup cycle. But that's not the only thing that'll make it run.

If you regenerated so much electricity before stopping, it'll use the battery and MG to spin the engine without running the engine in order to get the battery SOC back down to a healthier level. That would be indicated by the battery indicator being filled up on either of the screens @alanclarkeau posted. This can happen if you live at the bottom of a hill and/or made several brisk stops in quick succession.

 

I agree with Jerry. Often after I come back from being on the motorway, by the time I pull into my garage the engine is spinning as the battery gauge is full due to the fact I have a long downhill run before I turn into where I live.

I just let it do its thing, which usually results in the battery gauge dropping 1 bar before it stops running.

 

Yep. Don't worry about it. I soon learned that PRIUS only tells you what, in it's opinion, it thinks you NEED to know.

 

The answer has not changed.
Yes......maybe.......if it only persists for a short time, then nothing to worry about.
Making the car move and putting power into the battery are NOT the only two reasons that the engine runs.