Stuck in B?

You have a brake problem. Sounds like the pins froze up a long time ago, causing premature wear on your pads and it has got down to scoring your rotors (thus the sand, grinding feeling). That is my first guess. Hope this helps. If it is the brakes, I would seek a mechanic who knows how to work on Prius brakes as it is a very special process!!

 

By the way, if you are handy with tools or mechanically inclind, you can do this yourself. The most important thing to do before you do anything is to disconnect the battery!! If you don't you could have the pads move while you are working on the car. There is a complete "how to" somewhere in Priuschat. Depending on what is actually damaged, your cost to do on your own would be a range of $200 to $500. It could be a lot less, but, until you see the problem, I don't know what your costs could be. Good thing to know is brake pads and rotors do not cost an arm and a leg. My quote is factoring replacing all four sets.

 

Why am I seeing an add at the bottom of this page for enrollment to a local college, with a picture of pregnant enrollee, written in Vietnamese?

 

You’re computer may have been compromised with unwanted ads due to visiting adult rated websites.

 

Well the first sign of trouble, was the FIRST sign of trouble.
If and when you had that grinding sound in B, that was the gremlin revealing itself. Unless you have coffee beans, a grinding sound is never good.
What is happening right now, I'd be willing to bet IS connected with that very first grinding sound you heard. But it's too nebulous for me to even offer a speculative diagnosis.

If I was guessing this is transmission related.
The Prius transmission is an eCVT, actually a planetary gear configuration. I would speculate it isn't a rudimentary car knowledge project.

Could it be brakes?
Yes, it could be. But your total description of what is happening makes the diagnosis of transmission or brakes nebulous. I would think that if it was brakes related, your action of shifting back and forth from D to B, and B to D, wouldn't have any impact.
And usually with Brakes, if it's rust or any materials stuck between the pads and rotors, it kind of rights itself with some heavy braking.

Maybe my FIRST question should of been "Where was the grinding sound coming from?" Did it sound like it was coming from the Brakes? OR was it a grinding sound coming more from the center of the vehicle?

In either case, the symptoms would suggest to me, that in light of an admitted only rudimentary knowledge of cars, unfortunately you probably do need a mechanic. And when I say that, I mean a hybrid trained technician. IMO both the Brakes and Transmission on a Prius are Hybrid integrated components best serviced by technicians familiar with this reality.

 

I don't know.
For a long time I got repeated banner ads exclaiming that I was 1 click away from Asian women in my area that "Wanted to meet me."

I can't even bring myself to use Grub Hub or Uber Eats for Asian food, let alone click on a very questionable "dating site".
I suggest 1st ignoring, 2nd, a good vetted Ad Blocker.

 

any mechanic can look at your brakes. just remind them that if they need to do any work, they should follow the service manual if they haven't done prius brakes before, because they are electric. but no big deal.
if you plan to diy, just jack up each corner and spin the wheels to see if anything is binding

 

That would make sense, except the add wasn't "adult" oriented. Just a legit add for local college enrollment online. Thought it was funny that the person holding the laptop in her lap was pregnant and all the writing was asian. Only thing that was in english was the name of the College.

 

But the grinding is still there? My bet would also have been the brakes. Maybe a stone got stuck between the rotor and the caliper?
When was the last time you had your brakes checked or serviced?

It is unlikely that the B-mode is the culprit. The only thing B-mode does is tell the computer to run the engine to generate brake force. No gears are shifted or any mechanical stuff is going on.

 

are there any trouble lights on the dash?

 

no idea how that affects anything...

 

Parking brakes must have not been disengaged completely. America’s tires Didn’t disengaged the parking brakes on my car when they drove it to the lift and back to me outside waiting. At first, I heard sand like grinding sound incredibly loud coming in the direction where I parked when they were pulling it out to the lift as engine reved loudly. As they drove it to where I was standing to pick up, same sound. I got in the car and saw parking brakes still on with the “brake” lit in red. The parking brake wasn’t fully disengaged. Perhaps basic car training is only a suggestion for those tire companies.

 

Toyota's foot pedal implementation of a parking brake on a regular passenger vehicle is odd too (one of several oddities). These oddities make the Prius and valet drivers a poor mix.

 

1. Consider not using "B" mode...or at least not much.
You live east of the Rockies, and you used to live west of the Rockies, so it ought to be pretty easy to figure out why.
There's no real efficiency advantage in compression braking (squirrel topic!) and if you know how to use regenerative braking you're already using your traction battery as a waste receptacle.

2. You're closing in on 10 years and 120,000 miles.
If you KNOW you're going to keep your car for 5 more years then it's time to make some important maintenance decisions with your car.
Review some of the threads on trans-axle fluid flush, throttle body cleaning, and EGR cleaning.

3. If you decide to ignore (2) above, do a keyword search search for "head gasket"

Good Luck!