Car Shut Off / No Start - CEL Codes UO293 / B2799

2008 Prius, 252k with no prior mechanical issues or CEL’s. No aftermarket bulbs or sound system. Only thing I have is a OwlCam that is always plugged to the OBD2 port and a USB-C cigarette lighter conversion (both on car for about a year).

Today it abruptly shut off on me while stop/go at a stop sign. The car just died and nothing on the dashboard. I started to smell a burnt wiring smell coming from the car as well. I thought it was my 12v battery but a quick check and it was fine, Hybrid battery looked ok and have not been having any issues with it and charges fine. So I attempted to start it up and nothing, I would press the Start button but nothing happen. I went on to check the fuse box under the hood and found the AM2 fuse blown and all other fuses were ok. I also checked the wiring for frying or damage and it seemed all ok BUT the burnt smell appeared to be coming from inside the inverter motor. cover. I swapped out the AM2 fuse and it blew it again, swapped out another one and this time it didn’t and the car started up again. Decided to get it towed and will check it on my day off tomorrow but wanted some ideas as to what to look into as my “Electrical Skills” are almost non-existant. The CEL was also no on and got the UO293 and B2799 codes. I cleared them just in case.

2 notable things id like to mention just in case is that twice in the last 6 months, the combo meter display has gone blank but after some research suggesting to disconnect/connect the 12v battery and display has come back on, I have left it alone. 2nd, the red light on the key fob has started to blink and will no longer work from over 20 feet away (perhaps a dying 2032 battery).

Below is what my Blue Driver scanner showed:

 

I did look it up but wanted to get more insight as some say you would get a p0A93 codes when its a bad inverter pump and I am getting the UO293 code. Also, some say it can be the combo meter causing the issue, odd noise from the inverter (which mine doesn't have) and others even said a bad HV battery so the references are all over the place and was hoping someone would have had an issue closer to mine.

Also, B2799 code anyone experience that?

Suggestions welcome.

 

You may have missed that the AM2 fuse blew once after replacing it and not the second time it was installed. Would it need to continuously blow every time replaced if its the inverter pump for sure? The AM2 fuse is fine now and car starts and works fine but I do get a weird smell coming from inside the inverter (like a burnt plastic-ish smell).

Now, as far as oem vs aftermarket I can agree that OEM is the way to go, but are those aftermarket ones any good as a temp solution? I guess I would want to make sure it was the pump before shelling out $150+ on an original one. Aisin appears to be the OEM spec part but I see others like DORMAN, GATES, SKP etc… Any of them worth buying to test out and ensure its the issue?

Finally, when the car is on, MUST there be a visible coolant flow at all times at the reservoir to indicate the pump is working?I checked mine and the coolant is stagnant at FULL level with no movement. Perhaps this is the key to knowing if its a bad pump or not.

 

UPDATE:

I removed the pump and determined the burnt smell was coming from inside the pump itself, is this normal or indicate a definite failed part. I shaked the pump around after removal and sounds like something is loose inside, is it suppose to do that or not?

By the smell of it, it may indicate a possible shorted part and this way I would def purchase an OEM one as no need to test if the above indicates a failed pump.

Also, should the coolant be flushed and re filled due to this possible contamination of the fluid or would it not matter and simply refilled/burped once I replace the part?

Thanks in advance!

 

"electric ozone smell lightly burning circuit board” This is the BEST description of the smell anyone could have come up with. It should be in the dictionary when attempting to describe such smell LOL!!! You sir, get kudos for that jajajaaa!!

But yes, that along with a stagnant reservoir fluid indicate it to be the culprit. A buddy of mine has a tested and good one hes gonna give me for $50 so Ill probably do that as I called my local Toyota dealer and they want $190! Yikes

 

Not that I know of, I have only put 30k since I bought it. Do you know what the capacity is? I have about 3/4 left from a Toyota pink fluid gallon wondering if thats enough to flush and fill.

 

Got the one off my buddy and its OEM. Ill install that and keep an eye out for one but at least my car should be mobile again. BTW, i was getting that $191 price at Envision and $212 at Penske Toyota so went to RockAuto and found the OEM Aisin p/n WQT-800 for $111 after taxes and shipping so will be ordering from them in a few weeks.

Will post results after I instal this and hope all goes well.

 

figured its good to carry it in the car in the event this ever goes bad. But yes, used one is going into the car tomorrow

 

So, I installed the supposed good (tested) pump, connected electrical plug, topped off fluid and installed hose from bleeder valve to reservoir in case any air got inside and nothing happen when I put the car in AUX mode or when I started the car. There is no flow in the reservoir it's just stagnant fluid as well as no noise coming from the pump itself nor any fluid flow in the hoses. Could this have been a bad pump after all or something else? I am ready to just order the new Aisin pump but want to ensure I am not missing something which I doubt.

I checked the AM2 fuse and its fine. Is there any other fuses I should check or ??