Did our transmission just go south? P0AA6, MG2 in car replacement!

Its possible, I went ahead and did it. I tested the stator at the coil leads and it still failed, that ruled out the orange cables going down to it. The stator was pulled out, I had got a used one from a wrecker and it is now sitting in the car. Sealant is curing and WS fluid should be here tomorrow. With a little more assembly I will be able to report if I was successful.

 

Haha, I read "muddy the waters" and i thought about how the WS fluid turns into muddy water the moment you pour it into these transmissions!!!

 

I did have to buy a complete used transmission to get the stator, there was one at a local salvage yard and they only wanted to sell the complete unit. I was able to also test the MG's on the used unit so I had a great reference for what was different.

I'm pretty sure I would do a few things differently if I ever do this again, but I removed the under car spash guards, the wiper cowl, the inverter and tilted the engine trans to clear. I'm still in progress on this project, thats why my posts are not overly detailed, I am going to come back and fill in my process cause I have a feeling others might have to deal with this too.

 

I just uploaded the video I made where i show how to use an insulation tester, sometimes called a megger tester, to troubleshoot the P0AA6 code. I'm no video professional so please excuse the amateurness!!

 

Those 3 cables go down into the transmission case, and connect to the MG2 stator. They needed to be disconnected from the inverter to isolate, and because of seeing these results, I then disconnected the wiring in the transmission and basically tested again from there to isolate the wiring from the stator itself.


Here is a bit of a legend I created to show where the connectors are on the inverter, I disconnected the wiring to the different MG's or A/C and HV battery to test. To test the wiring going back to the HV battery you need to also disconnect the battery cable from the HV battery pack.

 

I made a write up for anyone else needing to do this repair. I'm still sorting out my pictures and notes but feel this is a pretty good walk through for going to the next step of stator replacement.

EverydayJasper: Gen 2 Toyota Prius MG2 stator replacement, P3009 P0AA6 repair procedure

Update on the car, several weeks and 2000 miles, everything is working! No more error codes!!

 

I dont know if I can insert the HTML code, so here are the procedure steps I wrote up, more details and pictures are in the post link above!

If anyone is having to go through this or needs more info ask! I'm happy to help out!!! I was a little disappointed with some of the responses I got when asking about doing this repair. Rather than taking it in or replacing the whole transmission, here is proof that its not too bad and doable in the car with just a jack and jackstands.


Before you start:
1. Remove HV battery service plug

2. Disconnect 12v Battery negative cable


Getting started
1. Remove wipers and cowl
2. Remove inverter cover



This is when you want to do your testing before getting into it anymore. You can easily test the MG2, MG1, A/C compressor and HV battery wiring. The steps continue down the path of MG2 replacement, because that is what failed the tests for me.


3. Loosen the 5 lugnuts on the drivers side front wheel.

4. Jack up the car, you only need to get drain pans to catch fluid and to remove the drivers side tire. Use safety jack stands under the body of the car!!!

5. Drain inverter coolant (this was a large bolt, maybe 24mm)

6. Drain transmission fluid (10mm allen head)

7. You likely disconnected the main (orange) electrical connectors from the inverter, now it is time to remove the rest of the electrical connectors.

8. Disconnect coolant lines from invertor

9. remove the 3 bolts holding the inverter to the car and remove the invertor.

Now we are going to lower the transmission to get access to the side cover


10. Remove drivers wheel

11. Remove the wheel well liner from the drivers side (requires removal of the front under cover too)

12. Put a jack under the transmission and give it some light support

13. Loosen drivers side sub frame bolts

14. Remove transmission upper mount main nut

15. Remove passenger side upper engine mount main bolt.

16. Disconnect black ground cable from transmission to fuse block area (it has a connector)

17. Lower trans with jack, as low as it will go.

18. removeoil pump coverin middle of transmission side cover (5 10mm bolts)

DO NOT REMOVE the x3 12mm bolts further out from the oil pump,these hold the speed sensor and it do not need to be removed at all.

19. Pull out pump drive tube, oring seal and gear. They easily slide out. Looks at the orientation of the tube, it has longer tabs towards the outside of the trans. I like to keep the orientation of the gear to the cover too, since it has broken in this way.

20. There are 2 electrical connectors that you need to disconnect from the transmission. One on the side cover, and one very close to it on the front of the case. Remove the 10mm bolt holding it to the trans. And slowly work out the oring. Then disconnect a smaller clip in connector from the transmission side. (these are just wiring pass through seals and connect on both sides) The interior wiring will be pulled back into the transmission case when removing the stator.

21. Remove the outer 12mm bolts of the side cover and use a soft blow mallet, screw driver or pry bar to tap on the areas you can as it takes a little work to get the cover off. Try to work evenly as it slides better when you don’t bind it. All the bolts are clearly visible from the side, you are working against the sealant and dowel pins.

22. With the cover off you can remove the rotor, it pulls straight out at this point only being held in by the magnets. There could be a spacer installed on the outside end of it. Sometimes it stays in the side cover when you remove it, sometimes it stays on the end of the rotor. Notice it and put it in a safe place. Because we are reusing the original side cover, rotor and transmission, this measurement doesn’t need to be changed and the same spacer must be used!!! It will take a good strong tug straight out to get the rotor out. Its got some weight to it too, be prepared and wear some clean work gloves cause it is also sharp.

23. Remove the high voltage power cable bolts up top (2 o’clock) from stator x3

24. This is time to check if you have enough clearance to remove the stator. Its going to need to drop as far as possible to get the clearance. The jack under the transmission doesn’t need to support anything, the transmission case is going to bottom out on the subframe. That’s why we loosened the subframe bolts, run them out to where they are in about 3-4 turns, it should be about 1 inch of clearance on the bolt, and use a pry bar or pickle fork to leverage the subframe down. This will be just enough clearance to get the stator out.

25. Remove the 10mm bolt holding the temp sensor to the transmission case at the 7 o’clock position, make sure the connector is pulled back inside the transmission case and free to slide out with the stator.

26. Remove long 12mm bolts holding MG2 in x3

27. Slide entire MG2 out, its again decently heavy, some might want to have a jack or something to land it on as it slides out. If you don’t have the clearance pry down some more on the trans / subframe. It will just clear! I did bend one tab on the the frame rail to give another 3/8 clearance.


That’s it! Removed!! Installation is reverse!



28. Get your used MG2 and replace into your transmission case.

29. Install the x3 12mm long bolts that hold it to the transmission case Torque spec isn’t supplied, I used 25NM or 18 ftlbs as that is what the bigger 12 case bolts torque to.

30. install the 10mm bolt holding the temp sensor to the case, and arrange the sensor wiring so it goes where it needs to (the whole in the front of the transmission case) Torque 5.8 NM or about 50 inch lbs.

31. Connect the 3 HV leads at the 1 o’clock position of the stator, These really only fit nicely the one way, but if you for some reason messed up their nice positioning, you need to figure it back out. It does matter. This torque spec isn’t explicit, but I did 8.5 NM or 71 inch lbs. (specs for MG1 connector)

32. Check the bearing / spacer that the rotor fits into inside the transmission, make sure it is all nicely stacked, coat it with some fresh transmission fluid to ease installation. Also coat the inside of the stator with some trans fluid.

33. This can be a little tricky, but the rotor (use your original one!) slides right back into place. Its decently heavy and the magnets try to fight you! Slide it in, if you are lucky it will drop right into place, if not you need to give it little twists and adjustments to get it to engage the gear and go that last inch. Wear your clean work gloves, be gentle, but also forceful. Don’t use a hammer to tap it in, you just need to align things and it will slide in.

34. Place the spacer on the end of the rotor

35. Install the side cover.

a. Clean both the mating surfaces very well.

b. Replace the O-ring on the oil pickup tube

c. Use a thin coating of sealant on the side cover, spec is 0.5mm thick

d. Align the side cover and tap it on to the dowels. The oil tube aligns first, then the dowels

e. install the 12mm bolts

f. torque to spec 25NM or 18 ftlbs

g. Allow 12 hours for sealant to cure before filling transmission.

36. Install the 2 connectors on the transmission, one on the front, and one on the side cover. Torque 5.8 NM or 51 inche lbs.

37. Install the oil pump drive shaft. Coat it with clean trans fluid. The more cut out end towards the outside

38. install the oil pump drive gear and driven gear, I like to try to make sure they go back in the same way as removed.

39. install the o-ring seal and oil pump cover with 5 10mm bolts. Lightly coat the threads of the bolts with rtv sealant. Torque to 5.7NM or 50 inch lbs.

40. Raise the subframe and retorque the bolts. Front bolt torque 113NM or 83 ftlbs; Rear bolt 157NM or 116 ftlbs

41. install the bolt on the drivers side engine mount.

42. Install the nut (80NM or 59 ftlbs) (its easier to remove the mount, place it over the bolt, and install than to try to force things to align)

43. Connect the black ground cable to the transmission to fuse block


At this point its no longer MG2 specific and you can go in the order you prefer.

• install wheel well and under liners, drivers wheel, and lower car
• install inverter (3 bolts torque spec 11NM or 15 ftlbs) and inverter cover (torque spec 21NM or 8 ftlbs)
• install wiper cowl
• fill coolant with about ½ gallon of Toyota super long life, use the bleed procedure. Drain plug torque spec is 39NM or 29 ftlbs
• fill transmission with about 5 quarts of WS type fluid through the fill hole, I like to use a suction gun for this. Fill plug toque spec is 39NM or 29 ftlbs
• Install radiator cover

And finally, double check your work, remove tools, connect 12v battery, then install service plug.