Today my Prius c will not go into EV mode so I cannot use battery power nor will the engine shut off at a stop light and when I let off the gas it throttles up for a moment what could be the problem
What you describe seems to be that either the ICE was not up to operating temperature or the traction battery was low so the ICE will not shut down at a stop and will actually rev up until the battery level rises. Either case what you described seems completely normal.
It definitely does not seem normal this is never happened before and it's 95 degrees here and was already warmed up.
That probably isn't a good way to describe it. The little C warms up VERY quickly........unless it is VERY cold outside. And the HV battery being that low is not "normal" at all. I think it likely IS a symptom of some kind of fault with the HV battery.......either cells going bad or maybe overheating. Regardless, I would think the condition would be accompanied by some warning lights.......unless the condition only lasts for a few seconds or minutes. Both mine have done that once in a great while but only briefly and with no fault lights; then it is fine again for many months. If it KEEPS doing it, it definitely is NOT normal and you need to have a dealer check it out.
It acted up on three consecutive trips so far today. The first of which was 11 minutes it was already warmed up from a much longer trip and it's 94 degrees out the second two were also when it was warmed up has almost 100,000 miles on it never happened before in 5 years
But you still have not mentioned the most important part: Are there any warning lights displayed on the dash when or after that happens ?? Edit: OK, no lights. You need to have this checked out. If a main connection is going bad and is overheating, the next warning might be a FIRE. Then......things work fine for a long time, right up to the instant that something goes wrong......and then they don't work. "Never happened before in 5 years" is pretty much meaningless.........except that it indicates that something is wrong now.
I'm not convinced that he has a fixable problem. I have never been able to get any of my C's to stay in EV mode for more than a few seconds when I wanted them to. I've heard that coasting at ~ 5 MPH in a traffic jam will do it........but I never see that situation. Then, it is REALLY HOT here now and my '17 kind of acted like that today. There were a couple of times that the engine rev'ed a bit when I was just sitting still.
When the battery is hot, I've noticed that it feels like my transmission is "slipping". I know this is just a protective measure and it goes away when I crank the AC up to max.
My C also acts like this sometimes since new, that is why I said it seemed completely normal behavior to me.
Mine does this sometime when the cabin air temperature is hot AND either the HV battery cooling fan/filter is clogged with dust or there is something covering the air intake. In my case, my back seat is covered with a towel and the seat is folded down. Sometimes that towel slips down and covers up the fan intake or I may have groeceries or something else blocking the air flow. I think the car does this to protect the HV battery from overheating. When it does do this, I've not seen any warning lights or other errors or CEL, but the ICE stays running when stopped.
