Master, engine, VSC and engine lights all came up at the same time

Yes, but the OP won't be able to do anything about her car's problem without visiting her dealer since she says local repair shops won't work on hybrids in post #1. Her car's problem is not a minor one.

Since she reported very little fluid turbulence in the inverter coolant reservoir in her post #13, it is possible that the root cause of her car's problem is a failed inverter coolant pump or the need to purge air out of the coolant system. This may have caused the inverter to overheat and the DC/DC converter to fail solid.

Sometimes the DC/DC converter will resume its functioning after the inverter has cooled down. This apparently is not the case with the OP's car, since she continued to get low voltage readings on the 12V bus when the Prius was made READY, last night.

 

I was reading this thread this morning and my wife thought I was chatting it up with another woman online. That selfie picture the OP has on her profile is really distracting.

Back to the topic, it's great how Patrick is able to diagnose the car. I knew the voltage readings were off but didn't know the cause. Wonderful learning experience.

 

When you disconnect the battery, the ECU computers all reset and you are able to drive the car until the computer detect the problem again. Disconnecting the battery does not solve your problem.

I think Patrick had ruled out your battery being a problem with a 12.4 voltage reading when on. You didn't need to replace that battery.

Has your car done the recall on the inverter water pump?

 

Where did you bring your car for service? Hybrid shop?

What is the VIN# on your car? I'll help you find out if you've done the recall on the inverter water pump

In November 2010, Toyota announced a “Limited Service Campaign” (number A0N) to replace inverter water pumps on 04-07 Prius. The reason, they stated, was the possibility of an air bubble getting stuck at the pump, reducing flow and causing the inverter to overheat.

 

Nobody is judging you, I mentioned what my wife thought when she saw me respond to your thread with your picture on it.

 

This is on the history of your vehicle, dated 1/11/14

CUSTOMER STATES THE CHECK ENGINE LIGHT HAS ACTIVATED. DIAGNOSE A ND REPORT. ~|~CODE P0A80 AND P3015 FOR WEAK HYBRID BATTERY ~|~WILL NEED TO REPLACE AUXILLAR Y BATTERY $239.95+TAX AND HYBRID HV BATTERY $2998.95+TAX CUSTOME R DECLINED REPAIRS AT THIS TIME. CUSTOMER ADVISED VEHICLE WILL B REAK DOWN SOON.

 

your car has an extensive repair record with Toyota, it's been well taken care of. All recalls have been done. I'm assuming you purchased this car after 1/11/14, the only reason the previous owner sold the car is because of the P0a80 code diagnosed by Toyota, which means the hybrid battery needs replacement. It mentioned the 12v needed replacement as well, so not sure if they replaced it before you bought it. But since you replaced it again today (hopefully with a proper AGM type battery), it shouldn't be an issue anymore.

 

You can access all the records for the car yourself. Go to Toyota.com, click on the "owner" portal. There you register and add your vehicle with the VIN#. All the information is there for you.

 

Napa has a $900 battery? Warranty on it?

 

You should also verify that your DC/DC converter is working properly. If the battery readings you mentioned when the car is "Ready" is correct at 12.4 volts, you might have a bad part. which is another expensive part. Hopefully it's just the battery that's bad and not more.

 

What's strange is that you were able to drive your car for a few weeks without problems. I'm wondering if the previous owner actually did repair the HV battery before selling it to you. Without properly diagnosing this car, you could be buying a battery prematurely.

I don't want to suggest the battery is bad based on a service record from Toyota. Just want you to be aware, this was a recent problem in January. $900 is a lot of money if that's not the cause of the problems you are experiencing.

 

FWIW, I would take the time to visit a Toyota dealer and pay for a diagnostic to have the codes pulled BEFORE I ordered any parts for your car.

So far we have learned that the inverter does not seem to be functioning ALL of the time. This could be caused by the inverter pump not working properly. Remember you did say you saw bubbles. No bubbles should be present. Also you did state that the voltage was 12.4 in Ready Mode which would demonstrate that the DC to DC converter was not working at the present time.

Furthermore, you have reported that the fan in the back is running and can be heard. That also indicates a possible problem with the battery, but could just mean that it is hot because the fan motor is plugged up with lint. The P0A80 codes does demonstrate a battery problem and the P3015 does demonstrate a weak module in the battery.

To make a long story short, I have a feeling that you have more than one problem that needs to be addressed.

IMO, it would be worth the money spent to pay a small diagnostic fee to Toyota BEFORE proceeding with ordering any parts or attempting any repair on your car. Throwing parts at it is not the way to try to fix a car. A proper diagnosis before hand is generally the best approach in any vehicle repair project including your Prius.

Don't be surprised that in the end you pay for a new 12 volt battery, a new or rebuilt traction battery, a inverter pump or bleeding thereof of the pump. Since you have stated that the voltage rose to the normal amount the following day it appears that the inverter had shut down due to overheating. This happens when the inverter pump is not operating properly.

I wish you the best of luck with your Prius. Sometimes this is what happens you buy a used car. It seems pretty evident to me that the seller sold the car knowing it had problems, but did not fully disclose to you the history of the car.