I'm rolling down the freeway in stop and go traffic, so I have been EV stacking. Clicked from EV to HV several times over the course of 5 minutes. Then, I hear this fairly high pitched revving sound - even and costant rev up, not rev/idle/rev. I thought it was the truck next to me, so I turn down the radio and away from the truck but it happened again. I would stomp on the gas for a moment, and it would subside - not completely because it would start doing it again very soon. I'm not accelerating, but it would be like throwing it into neutral and revving. When I come to a complete stop, it would not go to EV - the light isn't on like when it is warming up the ICE. My exit was coming up soon, so I would alternate pumping the break and gas to get it to stop. Only when I was at the light that I powered off the car to reboot. Since then, it did not reoccur. Strange... Perhaps related, but I doubt it - I had bumped into a vehicle around 3-4mph the day before. I was... drowsy.
So, when you stomped on the gas, the RPMs would drop? But the car would still move forward? And then mysteriously, the RPMs would rise again? And the only way to get it to settle down is to stomp the gas? At any point does the ICE shut off prior to you rebooting the car?
It sounds a lot like you were using engine braking. Read this: B under the D in the Drive gears? | PriusChat I am not sure when a PHV wold use the engine as an air pump.
The high-pitched whine is the most disturbing part. The components of the trans-axle are protected from over-speed, and you shouldn't be hearing that. You say you had an impact, so maybe a valve or actuator got stuck somewhere. However, I find it hard to believe that the computer wouldn't produce a warning about it.
I don't experience the revving you describe, but I do experience the ICE refusing to shut off even though it's warm and I'm not pressing the gas or in EV mode under 44 mph. Sometimes it just gets confused and stays on for a minute or two. Other times I can't get it to run. I'll be in HV mode and give it gas and the EV light stays lit even though the indicator is all the way to the right. Who knows? It's not perfect.
Sounds like what happens when the HV battery gets full or gets too hot to accept more charge. You were straining it in stop and go traffic, raising the temp and charge. Once it reaches a threshold it will take some charge then when stopped spin the engine at very high RPM to burn off excess power and drain the battery pack.
When I stomp on the gas, it revs up higher, but then spins down to an idle after I've let up on the gas. It revs up by itself when I was at a standstill-braked, or when I'm coasting. I was on the freeway, so it had full warmed up. Ambient temp was about 80 degrees too. Yeah, it didn't sound normal which is why I thought it was one of those loud trucks at first. When I was coasting, it was only around 25-35. I have a service appointment in a couple weeks, so I will be having them check it out and update here. I think I've experienced it not turning off like you had once, but not the latter. I had about a 1/3 charge left on the battery, and it wasn't warmer than other days. If I strained it, it doesn't seem like I did much, so I don't know about that. I've rolled it down a long hill to get 3mi of charge several times without any strange behavior. I haven't had it reoccur today, so that's something. Maybe a fluke?
When you say "1/3 charge left on the battery," are you referring to the EV battery icon or the segmented "old Prius" battery icon after EV is depleted? If the latter, I could easily see this as an attempt to recharge the battery. Even in such states, with gentle application of the accelerator you could, in stop and go traffic, travel under EV power.
It would be the EV battery charge. I had about maybe 2-3mi of charge. Even if it was trying to charge the battery, it would be a steady idle. This one was revving upwards in RPM. Hasn't happened since this first incident. I think it was from me switching back and forth too often. At least I hope that is what caused it.
