First, I'm a girl and not a mechanic but I work on my Prius bc I adore it. Basically, my car doesn't shift well it seems to get stuck sometimes and sometimes going down a hill it sounds like the engine is revving up. It has 194k miles on it and I bought it used. I don't know what maintenance was done before 140k. Is there anything I could do to fix this problem? There are no lights on in the dash.
Check the fluid level in the transmission, check the oil level, check your air filters both ICE an cabin, Clean your MAF sensor with spray. clean your hybrid battery fan. Use Yoo Toobe for videos on all of the above. If you are unsure I would drain and refill the transmisson fluid. It should be bright red and not too dirty. I did mine at 100K and it was awful.
There's no shifting in the constantly variable transmission in the Prius it's one speed It's not a three-speed automatic like you're used to and your regular automatics that you've owned before. What you're probably experiencing here is a weak battery and one of the electric motors is not able to hold or something along those lines In my generation two which is like yours when my hybrid battery was failing I could step on the gas and make the engine or car rev up like a clutch was slipping but apparently as I understand it that's not what was happening It's like the electric motor can't hold itself and add assistance like it's supposed to because of the poor voltage capability of the battery this went on for about 6 months while I was messing around with the car doing other things The minute I change the HV battery which was corroded in failing this problem pretty much vanished so I'm pretty sure it has something to do with the electric motors not being able to have full power and adding the power it needs to the rest of the system as it needs and we feel it like there's something slipping or over revving or not able to hold the power I remember this very well this is just a few months ago.
It's nothing to do with oil levels or flow sensors. Normally when you go down a hill with your feet OFF the pedals, the car will try to slow the car slightly and recover some energy and store it in the battery. Once the battery is full, you can't put any more electricity in it, but the car still wants to slow itself down a little. So it alters the effective gear ratio (not quite a shift, but same effect) to spin the gas engine. It isn't burning any fuel, it is just spinning the engine like a big air pump to try to slow the car down a little bit. It's perfectly normal and isn't hurting the car at all. Some people don't like the sound, but that's just how it is. When a Prius gets old, the battery fills up more quickly than it once did. It gets tired sooner too. You'll hear the engine more in general. The cure is a new hybrid battery, but sometimes you can get an improvement by cleaning the battery cooling fan and ductwork.
If you shift to B, (which you should normally never do) you can recreate your symptoms that Leadfoot is diagnoseing. B is useful when depending a long slope. In your model, more than a 600 foot drop
Without BEING THERE and doing some tests, you don't KNOW that. So......stating that as though it was a FACT is not really being responsible.
I believe you on both counts but I don't believe they're necessarily connected. Go you! As others have mentioned, it's a continuously variable transmission. It's not the same as a "one speed" transmission; it is able to adjust so a whole range of engine speeds can go with the same road speed. It's just that instead of having some number of fixed steps, it can adjust anywhere within that range, and the computer running the car is regularly doing that to match different conditions. So you can be driving along at a given speed, and a fairly low note from the engine, but then start to go up a hill and hear the engine note go up, to provide the extra power up a hill. Matching a higher engine speed to the same road speed would be "selecting a lower gear" in another transmission; if you were driving a manual, you would downshift to do that. In the Prius you'll just hear the engine note smoothly ramp up, instead of taking a 'shift'. Over the top of the hill, the engine note would first go back down; you don't need that extra power anymore from going uphill. But if you start picking up more speed downhill than you want, if you had a manual you might again downshift, only this time you wouldn't be doing it to get more engine power. You'd be using as a way to use up the car's momentum in spinning the engine around faster, so you keep the car's speed down. The Prius'll do the same thing (only before it does that, it'll put recovered energy in the battery first, until the battery gets close enough to full it doesn't want to do that anymore). As Leadfoot said, you might hear more of that happening in an older Prius as a sign of the battery not having as much capacity as it first had. But it's still just the car doing what it's designed to, just with a little change to when and how much. Niels Blaauw put together a really clever video explaining all the stuff the Prius transmission is doing and why: Prius Hybrid Drive Explained | PriusChat
We had someone on here with this problem once and they forgot to mention that they had a huge collection of Covid masks hanging from it, which was the cause of the problem. Beyond that, can you better explain what part is stuck? Is it the actual position of the physical shifter? Or is it the position the shifter the dashboard screen says the car its in?
