Inverter Overheating, Power/Battery Issue or some other issue?

Greetings everyone on Priuschat, hopefully someone can help with this issue I'm having. But first some info of the issue and troubleshooting tasks I took.

About three months back, I ended up getting the infamous error P1121. Around the time, my Prius showed a couple weird anomalies such as lagging when attempting to accelerate, although these issues never showed up again, but they may be useful information. Anyways the check engine light went off and on randomly with the same error code over the course of the three months. I did not initially replace the coolant valve control related to error P1121, due to the uncertainty if it was actually malfunctioning or not.

Although about two weeks ago I experienced what I think is overheating of the inverter, related to error code P1121, in which my Prius A/C went from cold to hot, less air and the following lights came on: EV system warning (red triangle), check engine, brake light, ABS and also in other occasions the airbag light as well as maybe others. Following that was a continuous beep and "Problem" showing on the display with the transmission lock mechanism error popping up as well. Most importantly I could no longer accelerate and came to a screeching halt on a turn lane, presumably because the ABS system was inactive. After this situation, I had the oil changed on my Prius, which was low and was about time to be changed out anyways. Following that, I had no issues, except maybe the A/C acting up one time. It was only a couple days after that I experienced everything above again while leaving my work. Long story short, I got help getting my car to safely off the road and returned to work with a coworker till I could retrieve my car later that night. I was able to drive home. I had a few more occurrences the next day, albeit I was able to make it to my destination by turning my car off and on and letting sit for a bit.

With the heat in my area, I knew I needed to address the error P1121 now. At this point in time, my Prius, when started, would already display the EV warning light and check engine along with "Problem" on the display but could still drive. I ordered a new coolant valve control from a Toyota dealership as well new coolant from a local AutoZone and got to work. I replaced the presumably broken valve control, and while replacing it let the old coolant leak out into a pan. I then filled the radiator up while running the Prius in maintenance mode to make sure to get the air bubbles out of the lines. I also topped off (to the max line) on the reservoirs for both the engine and inverter. I used the same coolant, but I've been told and heard they use separate types, but also seen people use the same coolant in both. So I don't if this is a problem or not. I also did not bleed the inverter loop as I don't have the necessary tube to perform that at the time. Anyways following the replacement, I checked for leaks, drove around my neighborhood for a bit and the errors all went away and my Prius look fine. I went to work the next day and had zero problems. I thought I fixed the problem.

Following that day, which was yesterday at the time I'm writing this, I had to go to work again. No problems until I went to lunch when all of a sudden, all the problems came back. Luckily I was already at work so left it in the parking lot till I had to go home. The EV warning light, check engine and "Problem" remained on all the way home, but I stopped at AutoZone to get the code read again and it's P1121 along with P0A93. P0A93 seems to imply from P1121 but I'm not sure and that leads us up to now.

I've done research on both these again and some mention maybe to replace the water pump for P0A93 but that doesn't make since in relation to error P1121. I already replaced the coolant valve control related to P1121 and yet the error is still persistant. Some are also saying it could be air bubbles in the inverter loop and since I didn't bleed it yet, this could be a possibility. Some are also saying it could be the 12v battery, since power loss seems to be happening when the Prius has all these errors as the A/C goes low, head lights become dim, and the powered windows going down and up slowly. Although, I do not have issues starting the car and battery voltage seems to be fine. Last time I checked it was 11.7v in accessory mode and around 14 when on, parked. It's worth mentioning the 12v battery was replaced 4-5 years ago when it did have issues starting up but I'm not sure if it could be the cause now.

Anyways, given all the information, what might be the issue and what should be my next step of action?

Thanks.

 

I have not looked for turbulence in the inverter reservoir but I will as soon as possible. I have approximately 83000 miles on my Prius at this time. I don't think the inverter water pump has not been replaced by the previous owner but I know I haven't had it been replaced. I don't have a code reader on hand but my relative does but I haven't had any hybrid codes read as far as I know. Only engine codes from the OBD port by both my relative and AutoZone.

I have also did check the fluid level in the radiator as I was filling it after replacing the coolant valve control. I believe I had completely filled it as I could longer put any more in, as well no more air bubbles after about an hour of running in maintance mode.

Also just an update, I drove my Prius to work today again and no issues, not even errors, but knowing from previous experience it's still probably having issues but I figured I add this in. I'll see if I have issues going home tonight.

Thanks for the input, anything helps!

 

I've should've been more clear but I did top the oil off right after the first situation in which I found out it was low. I then had it changed a few days ago.

Also when replacing the valve control, I did remove the front plastic cover and filled the from the radiator cap. I checked the fluid the day after performing that to see if anything has changed and cooled down and it remained the same. I also checked it last night and it seem to have been filled still. I will double check it tomorrow morning.

As for the 12v battery, I don't have a charger on hand but I should add that it was 11.9 v now in accessory mode with head lights on (same when it 11.7v) but is 12-12.1 v with the head lights off. I will look into getting a charger for it to make sure it gets fully charged.

Lastly, I have gather some useful information, based on all yours suggestions. I was able to drive home fine but I inspected the inverter reservoir for turbulence, and other than vibrations from the engine, I did not seem to see flow of the coolant. I started and turned off the Prius a couple times to see if the pump would activate and see turbulence but I didn't see anything again. I decided to let it idle, parked and observe the behavior of the car in a controlled setting and periodically check the inverter reservoir for turbulence as well as any other signs of abnormal behavior. As I expected, roughly 15-20 minutes of idling, the Prius started showing symptoms of overheating and stopped functioning with all errors I stated before. The entire time I didn't see flow in the reservoir which seems to make it clear that the water pump (P0A93) is indeed not functioning. I hope this assumption is correct. As for the possible air bubbles, I will inspect the coolant level tomorrow and possibly follow Patrick's suggestion to see if that will clear error P1121 as well.

Any other inputs? Thanks once again!