Even after my TCHs gas motor (ICE) is fully warmed up, there are times that I would expect EV mode, but cannot achieve it. Here's an example:

Last night I drove 20 minutes to a shopping mall. As I looked for parking, I was in EV mode (no gas motor used). I parked, went into the store, and returned to the car in less than 10 minutes. I started the car, and headed out of the parking lot. The problem? Once under way, although still in the parking lot, I could not get the car to use EV mode. Even at 5 or 10 MPH, until I came to a COMPLETE stop, the ICE would not shut off.

This same scenario happens occasionally, even with well-charged batteries. It bugs me when I have to drive at crawling speeds with the ICE unnecessarily running, and I can see I'm just getting 20 MPG. Once I come to a complete stop, and only THEN move forward again, can I get EV to function as I would expect, at the same low speeds. Sometimes, such as on the freeway, it's inconvenient to come to a full stop, but it doesn't seem that it should be necessary, and most of the time it works fine, but not always.

Any ideas from experienced owners?

 

The only idea I can think of is that the ICE comes on at computer control after initial start up after being parked to bring the battery charge up to some preset level determined by the programming.

 

it could be that the ecu thinks that the catalytic converter cooled down and needs to be warmed back up. 20 mins may not have been enough time to get the cat sufficiently warmed up, esp. after letting it cool down for 10 minutes. when you're at a complete stop, the ecu may think that it's okay to shut down the ice even though the cat is not warmed up since no emissions are being generated.

just a thought

 

Good thoughts, but not the right answer yet...

It happened to me today under the following circumstances: After driving at 45ish MPH for about 10 minutes, I reduced my speed to about 5-10 MPH to match the slowing pace of traffic. It was impossible to completely stop, because the line of cars was continually moving, but the ICE would not cut out. Later, when I came to a full stop, it did switch to batteries. When I tried to replicate the incident by driving slowly, I couldn't. Sometimes it happens, sometimes it doesn't. I am baffled, but still happy that I'm doing 39 MPG on this tank, so far.

 

Maybe, you are in S3a stage known among Prius drivers.
http://priuschat.com/forums/kb.php?mode=article&k=14

Ken@Japan

 

Steve,

It's a killer watching the MPG gauge go all the way up to the top, isn't it? I assume the system knows itself better than I, so I try not to worry about it.

 

ken1784, thanks for the excellent link. I think you have found the answer, as it seems to perfectly describe my situation. Nice to know that everything I experienced is normal. I hope everyone will take time to follow your link, since it is such helpful information.

 

My TCH went into EV mode today with the cruise set at 40 MPH. It was only for about a 1/4 mile before I got to a red light, but it did it. It was not on a decline, in fact it was a little bit of a slight incline. Very surprising.

Also, after I left the red light, I set the cruise on about 38 MPH and it went into EV Mode again for a couple of blocks before the next red light.

Very cool and unexepected !!!

 

I have also experienced the exact same scenarios when driving. I have often thought that the car had its own personality and was like, "Ok im going to go into EV mode when I feel like it" kind of thing.

Honestly that is what it seems like. These things DO have a mind of their own..dont they???

But the article that Ken showed everyone here does make sense. It seems like when the car has been running for awhile, and when it is warm and it does finally get into that "EV ZONE", it is really, REALLY fuel efficient.

 

With the HSD, smart key thing, stability control, etc, I kind of expect a 2001 moment where David asks Hal to open the pod bay doors..."I'm sorry, David, I can't go to EV mode right now."