Engine seized? 118k miles

MG2 has to spin. That is the motive force that causes the car to move. MG1 is the starter/alternator

 

If this data is pulled during an attempt to start the ICE, then yes, 0 RPM is right. 4200 + or - on MG1 equates to 1000 - 1200 ICE RPM, which is a start attempt.

 

Busted damper or flywheel I'd guess. But ICE extraction required to verify.

 

It would be interesting to see what happens if you reach 42 mph on a drive.

 

That is the max speed available electric only. That should spin the ICE. Or show you the damper is broken.

 

Or wide open throttle from a dead stop in power mode. Either of these actions should show if the damper is broken.

 

This sounds more and more like a damper/transaxle issue. But it’s either drop everything out the bottom, or pull ice from the top, then try and pull transaxle out the top afterwards. The good news(if you can call it that) a car-part.com search shows them as low as a Ben Franklin. But that is a lot of work to do. Especially on a car that you haven’t heard the ICE run yet.

 

If the MG1 is the component that spins the motor to start, And if the MG1 spins but not the motor, it would seem to me that the connection is lost between the 2. Further, I once owned a '72 Chevelle that had a cracked flexplate/flywheel and it vibrated violently on acceleration. Also I could picture the crank position sensor fault if the ecu is expecting the crank to be turning when it is not.

I must say though that I am not a mechanic. Hoping that you are zeroing in on the problem and the solution. Good luck

 

So, if we power up by keeping foot off the brake and pressing power twice, are we able to clear the codes and have them stay clear? Doing it this way will ensure the car does not try to go ready or try to start the engine. If the codes clear, and stay clear, then foot on brake and press power to have car go to ready and it will try to start. If MG1 spins to start the engine, but engine doesn't turn, I'm sure the code would return since there would be no CPS signal. As mentioned previously, that pretty much narrows it down to a major mechanical issue at dampner/flywheel area.

 

When I unplugged my CPS, I could tell the engine was spinning. There was just no spark. Not trying to be a jackwagon, but if you hear the sound a Prius engine that starts like it’s supposed to, versus yours, is there a difference on that noise?

I have tried to time the response from power button to ICE running on my car, and it’s 1-2 seconds at most. Your techstream screenshots show 4-5 seconds of MG1 on time to the engine stop request. It makes sense that your car would “request” an engine stop due to not seeing the CPS signal.

The question is where is the failure in your driveline. I have searched this page and there are only a couple of threads on the whole site that even touch on the idea of transaxle damper noise/failure, and the O/P of those threads found the noise to be self inflicted. So did the M/G1 shaft from sun gear to damper fail or maybe the planet carrier? Can you just pull the ICE, and disassemble and repair that with the transaxle sitting in the car? Should you drop the entire subframe and change the entire transaxle as a unit? These are the unknowns, as this is likely the first documented time on this site this type of failure has occurred. I wish you luck, but I hope I never find myself where you are now good sir.

The WeberAuto YouTube channel may be your best friend right now. They have several videos dealing with the Prius transaxle.

 

Hopefully this helps (54:20)

There was a screenshot where MG2 revs are 0 and MG1 over 4500. This tells that vehicle is not moving(MG2 0) and engine is being tried to start by MG1.
At that state engine should be rotating, only way not to rotate is that clutch damper is slipping. That damper is to made slip under heavy load to protect. My bet is that one is problem?

And if you can move car in EV mode, then MG2 is rotating. Car cannot move without MG2 being rotated.