DIY Gen 1 MG2 Replacement P3125 P3000 P3009 P3191

First off my car just quit driving one day so that was my symptoms and I started researching the cause from there which turned out to be the transaxle. Well after spending multiple hours trying to narrow down all the info on replacing the MG2 stator on my 2001 Prius I decided to post up the process for what I did. Now I had to do this in my driveway with jack stands so that made it a little more work however it was very doable and didn't even need that many tools. This will be a brief explanation on the process with some points on what NOT to do. You can search how to remove certain things as I did not take pics of the jobs where others have already done write ups on them. All being said below the job would have been much easier if I had been able to get the transaxle a little bit lower as I was fighting a little with the frame when reinstalling the MG2. This is what I did and it worked out fine however if anyone has any other advice feel free to add suggestions.

1. IMPORTANT! Remove HV battery safety plug and then the 12v Battery neg cable!
2. Remove wipers and cowl
3. Drain inverter coolant and transaxle fluid
4. Remove inverter (search) this is to get at trans mount
5. Get car up in the air (lift or jack stands) Use safety!
6. Remove drivers wheel
7. Remove bolts from center mount under car
8. Put a jack on the transmission
9. Loosen all 4 sub frame bolts ( I ended up removing the drivers side 2 bolts)
10. Remove transmission mount bolts and main nut
11. Lower trans with jack
12. remove oil pump in middle of cover (5 small bolts) See pic with finger pointing DO NOT REMOVE the 3 bolts further out from the oil pump these hold the resolver I believe it's called and apparently that is timed at the factory so it will fall apart when removing the cover if you remove those bolts like I did! Luckily I purchased an entire transaxle so I just used that cover I also compared and timed the cover so should have a reference if anyone makes that mistake!
13. Pull out pump drive tube ( I don't know what the correct term is but it slides right out)
14. Unbolt sensor attached to cover and disconnect
15. Remove the outer bolts of cover/ then use a rubber mallet to tap on the areas you can as it takes a little finagling/wiggling to get the cover off.
16. Once cover is off remove power cable bolts up top from stator (3)
17. Remove long bolts holding MG2 in (3)
18. Slide entire MG2 out, this sucker is heavy so I slid it out onto a jack and lowered it down.
19. Go inside and warm up a bit in my case a brewsky was called for
20. I purchased a good used low mileage transaxle for $475 and the MG2 was perfect, this was a gamble but it's something you know right away when you pull the cover. Also the fluid was very nice. Harvest the MG2 at this time and set aside.
21. Check the pick up tube O ring mine was cut and there was lots of black slime in the area. This may or may not be the cause of the failure however I believe this should be a preventive maintenance item to check when you drop the pan. The pan is so easy to drop and check that EVERYONE should do this in my opinion.
22. drop the pan and remove the pickup tube/screen (1 bolt)
23. Clean everything, my screen you could not see through! I used brake parts cleaner and cleaned everything up nice.
24. Clean off FIPG (silicon) from mating surfaces and make sure no grease/oil is on either of them. I used autobody grease and wax remover but brake parts cleaner should be fine.
25. I pulled the rotor out of MG2 (well my father in law did as I could not get that sucker to come out as there is so much magnetic pull! WEAR GLOVES FOR THIS or you will cut your fingers!
26. Now reinstalling I was not sure if the whole unit should go in at once or not so after watching a Youtube time lapse I notices the MG2 was put in first then the rotor installed which makes sense because you can bolt in the MG2 and the stator will suck right in most of the way. The teeth need to line up so you may need to turn it slightly with a long screw driver like we had to. Also to note the MG2 and rotor together are very heavy so I was at first tryimg to jack it up and slide it out to no avail. Once we separated them I was able to just lay down and hoist each up and in way easier!
27. Reinstall top 3 power cable bolts
28. Pull sensor wire out through the mounting hole
29. Put a bead of Toyota FIPG all the way around the cover, you don't need a thick layer just use your finger and cover the whole area. The dealer gave me black but the original is orange however at this point I was not going to drive 2 hours to get the other color since it's for oil pans etc anyway. I did a ton of research on this as well and I would not skimp on this because if it leaks you have a PITA to redo the sealing after installing fluid. This stuff has a 15 minute work time so be aware of that.
30. Install cover, once again some finagling will be needed until it lines up correctly. Tighten all the bolts and call it a day so the sealer can cure properly. I gave it 16 hours.
31. Slide oil tube through until it locks in place, note the orientation longer notch outward if I remember correctly/install oil pump and cover.
32. Install new O ring on pick up tube and reinstall the screen/tube. Lube it up good with some trans fluid so it slides in as it's a tight space but a little wiggling and you will hear it sort of pop in place. Tighten up the bolt.
33. Install the pan with a new gasket.
34. Hook up sensor and reinstall back to mounting hole.
35. Jack up trans and tighten all sub frame bolts/mounts etc
36. Fill trans with 5 qts fluid
37. Lower car to ground and reinstall the inverter.
38. Fill/bleed inverter with Toyota coolant, I reused mine as the pump was just replaced 5k ago so fluid was still like new. This is another thing I heard took forever however it was very easy. Turn key to on and fill reservoir. Crack both bleeders and wait 5-10 secs. Do this about 5 times until the correct level and pump gets quiet. After that I just checked it and had to top it off a tiny bit over a couple days.
39. Reinstall cowl/wipers
40. Reinstall HV battery safety plug and hook up Neg 12v cable.
41. Turn on the car and hope to see no more warning lights! In my case all was perfect and I was very relieved. However now that I have done this once I could easily do it the next time. I am doing this all from memory so if I missed anything feel free to comment! Now you can save hours of time if you decide to tackle this on your own which many of us may need to do now that these Gen 1's MAJOR repairs outweigh the resale value of the car. I believe the Gen 2 is very similar and as soon as I buy my Gen 2 I'm pulling the trans pan and cleaning everything out as well as checking the tube o ring (assuming this is the same?) Hope this helps anyone who wants to tackle this job themselves. Good Luck!

What you need:
trans pan gasket
Toyoya IV transmission fluid 5 qts
Toyota FIPG
Toyota coolant
Brake cleaner
Tools, mostly 12 and 10 mm bolts

 

I have a parts transmission now if anyone needs anything. I was planning on scrapping it soon however thought may keep it around if someone has a use for it or some parts off of it.

 

I finally got the thing out of the back of the suv so it's in storage now. At the time just wanted the thing out of the way however after thinking about it decided that would be a major waste of a lot of good parts.

 

Mine made it to 180k so you are doing well. Like I stated I think EVERYONE should drop the pan and clean the screen and check the o ring on the pick up tube. This may be the little almost always overlooked 5c part that is causing these failures, or may not but seeing it quite often makes one question it. The nice thing is if you can do the work and have the trans if/when it happens it's not that bad at all to swap the MG2. I would do it again.

 

Telmo, first thing to do is get the codes and report back. MOST of the time only MG2 goes bad in the Gen1. I actually took apart the complete Gen 1 transaxle (and Gen 2) and found the MG1 to be completely encased in a what seemed like a plaster like (can't think of better way to explain) casing. In the Gen 2 the MG1 is just like the MG2 with just the transparent coating on both which seems to be what deteriorates possibly and causes voltage shorts or spikes and burnt motors? I wondered to myself why couldn't they have put the plaster type coating around all the MG motors or why was it changed...I think I know why but they are such good cars I can't bash them. I believe my 2 Gen had a bad MG1 so I suspect my hunch is right, if you have a 95% MG2 failire rate with the Gen 1 that has the encased MG1 it's pretty obvious what is going on. My Gen 1 would not move with bad MG2 and my Gen 2 would drive fine then throw the code and lose power so those are the differences in my case. Yes transaxles for both my gen1 and gen 2 however I bought them both that way so they turned out well. The gen 2 is now a taxi with 220k on the clock and driving like a dream

Also I think it would be very difficult to replace the MG1 unless you are a transmission specialist or take lots and lots and lots of pictures. I'm one who likes to do things others say is impossible However to be honest aster tearing down the transaxle I myself would be very nervous putting it all back together and hoping everything will be perfect. Doing just the MG2 is not that bad however that also accounts for the transaxle staying in the car, replacing both would require removal of transaxle. Good luck

 

I'm guessing here but gonna say G2100 like for MG2. All you need to do is order the "large" one if they are looking it up. Hope that helps.