Warning lights, P0A93, no AC, cruise, brakes not working correctly..

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Yes. These electric pumps don't last forever, and if it wasn't replaced prior, then it is due for such.

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Yes and you must be warmed up pretty good because 13.3 volts coming off the inverter to the 12 volt battery is a little bit low It should be around 14.5 14.4 so on and so forth as your inverter coolant heats up your inverter is throttled back to not overheat overcharge and damage more expensive parts so once you change the inverter pump make sure the AM2 fuse is good and the coolant is at the right level and it's circulating I'm betting your output to your 12 volt battery will jump up to close to 14 volts or you need to find out why it's not.

 

So, if the inverter pump fails, one of two things can happen. First is that the pump shorts, which pops the AM2 fuse and the car stops immediately and won't turn on. Second is that the pump just "won't pump anymore", eventually causing the inverter to get too hot and turn off.

Yours sounds like the second. Easy enough to confirm. Turn the car on to ready, then remove the cap on the inverter coolant reservoir. You should see coolant moving around inside. Ideally there would be some turbulence.

Many here on the forum recommend using a Toyota pump (from a dealer or other reputable source). Some have had poor results from using aftermarket parts, and places like ebay or amazon are known to have possibly counterfeit parts sold.

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That 12V is either severely discharged or is on the way out. I'm concerned more about the first number, which as somebody else posted above, is low. Fully charged the 12V should be at 12.7V (ish). It's possible that the 12V is so messed up that it is dragging the inverter voltage down. If the battery is reading <12V it cannot be tested because it is too discharged. You could get it charged up and tested, but if it is more than a few years old, just replace it. Walmart sells a battery in the right size and it may be more readily available (and cheaper) than an OEM battery. Let's see, where are you... Oh, Arizona desert. Yeah, the 12V is probably toast, batteries don't last long in that sort of heat (national weather service shows today at 109F there.) If the car is parked outside leave the windows down a bit, heat isn't great for the big pack either

 

When the HV control ECU sets a trouble code (whether because of an inverter issue or anything else), the brake ECU always sets a couple codes of its own, just because of that. Because the two ECUs have to cooperate to do regen or engine braking, the brake ECU just figures any time the HV control ECU isn't happy, he's not happy either.

One of the things inside the inverter housing is the DC/DC converter, responsible for charging the 12V battery. if that shuts down, the battery doesn't get charged.

 

At least we know you weren't in the ultimate fail-safe mode, which only acts on the front brakes and does nothing in the rear.

 

Brakes must be run by the 12V system? Replaced 12v, constantly beeping and no power brakes | PriusChat

 

Power brakes. Power has to come from somewhere to build up some pressure. The only belt on the motor drives a water pump, so mechanical pumps in the brake system are ruled out. A pump could run straight off the HV battery, and indeed the AC compressor does, but they didn't do it that way for the brakes. That leaves power from the 12V system: voltage/current from the inverter, 12V battery, or the box of capacitors next to it in the hatch area. If all three of those are gone, there is nothing to power the power brakes. Use up whatever pressure was in the system, and you are left with stomping really, really, hard on the pedal.

My first car was a 1965 Corvair, which had hydraulic, but not power, brakes. It stopped really well, at least for that era, and brake pressure to achieve a normal stop was not extreme. Never thought about how they managed that. Perhaps the unpowered designs gave better mechanical advantage for the brake pedal on the master cylinder, so that it could produce more pressure in the brake fluid for the same brake pedal force than a modern car, which expects a pressure boost from elsewhere.

 

My first car had hydraulic, but not power, brakes, and brake pressure to achieve a normal stop was not extreme. It was also about half the weight of a Prius.

 

The Prius uses a "brake by wire design" because it is a hybrid. That allows the ecu to blend regenerative and mechanical (friction) braking to achieve better efficiency.

So the brakes need something (besides your foot) to provide application force. Normal cars use vacuum or hydraulic boosters powered by the engine. That won't do on a hybrid when the engine is off frequently.

That leaves an electrically powered system. Toyota chose to use 12V for a pressurized brake fluid system. The pump doesn't use enough power to need High Voltage, and the 12V system can still function (at least for awhile) even if there are multiple failures on the car.

Interesting factoid, some other brands don't use a pump system at all for EV's or hybrids. Instead I have seen a remote master cylinder with a motor drive. So the the ecu just "steps on the pedal" to apply the friction brakes. Might have been on a newer Honda.

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For what it's worth, the gen 2 is the most brake-by-wire Prius generation.

Gen 1 had a sort of and-wires-too design where your foot on the master cylinder really does create some operating brake pressure, and banked-up pressure from the electric pump and accumulator enters in a 'booster' chamber behind the master cylinder piston and assists you. And after gen 2, gen 3 went back to a design like that. In a loss of electrical power, you still make brake pressure with your foot, and you even still get assist until the accumulator pressure is used up. (That can last for 20 to 40 strokes, way better than the 2 or 3 assists you can usually get in a car with a vacuum booster if the engine has stalled.)

But gen 2 went all in on brake-by-wire. Your foot only pushes fluid into a stroke simulator, making a pressure that the ECU takes as a control input, how hard you would like to brake. The ECU has the only control over the valves that send the banked-up accumulator pressure out to the real brakes. Because that control by the ECU is so crucial in gen 2, there is the box of capacitors in back to keep it powered. Only gen 2 has that.

The box of capacitors only keeps the ECU and the actuator valves powered. It doesn't power the accumulator pump, so you'd still use up accumulator pressure with each use of the brake, until there's no more. (Also, I don't know how long the capacitor box should be able to keep the ECU and actuator powered.)

There is a final level of fail-safe where the capacitor power has run out, or the ECU is flaky, Then a couple valves do drop open in the actuator and your foot pressure really does send fluid to the brakes—front only, with no assist (push hard!).

Something I looked at for the gen 5 Prius made me think they had done away with the accumulator completely: instead of a pump banking up pressurized fluid for use later, they just count on an electric pump doing the work each time you brake. Seems a little like that newer-Honda(?) approach.

 

Kinda similar, but the Honda uses a motor and gearbox to push on a piston in a "conventional" master cylinder.


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Looks like it might be a reasonably inexpensive part also and probably covered by a lot of the rebuilding outfits