This might be a long winded thread, but maybe someone has run into this before.. Back Story: I was driving on the freeway about 9 months ago the car had about 275000, car lost power, made it to my destination, but thought, i better get home. It was making a whiny noise like a Ford power steering pump of the 90s, made it a few miles and lost all drive, Triangle of death, didn't move. Got it towed home. I thought well, over a quarter million miles, the tranny is bound to fail, so I went to the wrecking yard, got another transmission. Everything seemed fine, in fact, I thought the car actually had a little more pep and was smoother. Fastforward: The car has about 293k miles now, and (luckily) I was just pulling into my driveway as the dreaded whine came back, then triangle of death. The only code it shows now is P0A7A on my cheapo reader. Same symptoms. I guess the question is, I notice that the pump is pumping coolant. So i had thought maybe i'm overheating the transmission and i'm using genuine Toyota transmission fluid.. Is my luck that I just happened to have the OG tranny die and then playing russian roulette I got another transmission that failed in under 20k miles? Or is there something underlying that is killing my transmission? I fear that at this point with almost 300k in a car that is ready to be sent off to the graveyard.. The rest of the car is pretty used up. (knowing that the batteries are on borrowed time, the engine has slight knocking at startup that could be rods) I was hoping in the back of my mind to make it to the 400k mark but now it might be better to part ways.
Take the transmission out of the equation and what do you have nothing some electrical cables some coolant passageways and hoses that's about it and drive axles and all that is still sitting in the car we just talking the transmission here so that's that any grinding winding weirdness usually winds up being inside that transmission unless it's obviously out at the wheel or something like that. I guess these are starting to show up in more numbers now with the high mileage so I guess there's always that. A whiner a groan like that you know could be a bearing a spacer shim that's worn down and out of speck and allowing too much end play which in turn is allowing something else to get too close to something else and this is the noise it starts to make initially and God knows how bad it will get going forward louder looking in the manual at the transmission in the repairs it's a lot of measuring three times to get it right and ordering shims in the sizes that you have added subtracted and come up with a thickness etc in about 5 or 6 places so they should be some notable play inside of those areas internally. I'm wondering when you pull your transmission back is their end play on that output shaft that's what goes into the torque plate on the back of the engine?
P0A7A is an inverter code, I believe. Has any thought been given to the inverter? I don't have a gen 2 repair manual handy. In gen 3, P0A7A has around thirteen different INF codes a good scanner can show you. I don't know about gen 2. I've looked in a gen 3 repair manual PDF that was floating around, and it's missing the actual P0A7A section with the troubleshooting steps. (The PDF probably got made by somebody signing in to TIS and clicking Print some soul-draining number of times, and they must have missed some clicks.) It has the summary table with the codes briefly listed, and other codes where P0A7A is cross-referenced, but is missing the actual section you would want. But again, that's a gen 3 PDF, and you'll be looking for gen 2 info anyway. Sometimes it really is easiest just to go to the source: Toyota Service Information and Where To Find It | PriusChat
Can the inverter make those whining and groaning noises electrically I guess I have no idea. And if that was happening it would seem like that would be because of insufficient output coming from a motor generator in the transmission to invert said power or something like that maybe. I know electricity can do some funny things or lack thereof when a circuit is looking for it.
Thank you! Maybe it is the inverter, electrical can make some weird noises. The whining noise is almost immediate before the car will stop moving. It isn't like i'm driving for weeks with the whine, it is a matter of half a mile, red triangle of death, then the car doesn't move. My thoughts were it was the MG1 or MG2 (I apologize as a car guy this car is a bit greek to me), but my understanding is those are the drive motors and they can unwind or get contaminated and short. While a transmission isn't the end of the world, they are cheap, maybe just the luck of the draw I got another transmission that was at the end of it's life too. (the gamble you take when you go to the junkyard). I just was worried if i take the time to do this again, that i'll get another 20k miles out of it and sitting in the same situation again because there is another underlying problem. Love the car (as a non prius guy), it has served me well, like any other Toyota. To my understanding Gen 2s are one of the best, but we are up against all of them are pushing 20 years old and they have high miles. I'm just losing faith in the car, which i drive hundreds of miles a week and I don't want to get left stranded. (That might be the real answer to my question of parting ways with the car) I'll dig deeper, get a real scan tool or run it longer until some more codes pop up and maybe upload a video. Just throwing it out there in the Prius world to see if anyone else has had this problem.
If some of the power transistors within the inverter unit is shorting or opening up, due to overheating, that can cause an electric motor to "whine" - incorrect power application. There should be a procedure to ohm out MG1 & MG2 to isolate a motor problem vs inverter issue. If it's a bearing issue the whine would be persistent and vary with speed. 1. Did you check the inverter coolant pump for proper operations and flow? 2. Did you refill the transmission per OEM specifications and the level still where you left it last? Hope this helps.......
If you are looking for a scan tool, take a look at this link, https://priuschat.com/index.php?posts/3290690 You want to chose a scanner that can communicate with all the ECUs in the car.
Most definitely get a qualified scan tool and no 20,000 miles on transmission is not normal even from the junkyard transmission problems really aren't very normal if you go over the 20 years of Prius on the web pretty much an outlier problem unless you have some kind of horrendous driving style or something but I can't imagine we drive ours pretty hard the gas mileage we get shows that but this is the Corolla family these cars are pretty heavy duty then go a long time with very minimal maintenance overall.
And do consider looking up the actual Prius repair manual troubleshooting steps specifically for P0A7A. They may be a lot more specific than "grab a meter and go see what you can see."
