P0A93 Mystery ...

What's Justice important when you install the inverter pump and you fill it up with coolant because you should have lost some nobody ever uses 3/4 plugs and blocks the lines as they...anyway you lost some coolant when you replace the coolant if you fill the jug up to almost full to overflow level it takes a long time for it to push the air out of the system and bubble up through the tank and level some people screw the top on so fast they create a big vacuum in the tank and the pump can't move squat. So when you plug up the pump and you turn on the car and you put your hand on the inverter pump I know it's hard to reach down there is the pump in fact humming and running? If no we need to check the a.m. to use under the fuse box and I guess it should have been checked before you started this adventure but here we are do you in fact have 12 volts going to that little plug on the inverter pump when the car is ready if no we need to find out why more than likely the fuse or possibly a bad inverter pump right out of the box generally not with Toyota but everybody else who supplies is part possibly I can't wait to see a Toyota one that's immediately bad out of the box I've replaced five of these as a matter of fact I've stopped using the pump you're installing and it moved to a completely different shaped pump the hose is fit but the pump is completely different shape made for another duty on the same car.

 

The coolant control (3-way) is for the heat storage tank for the ICE and had nothing to do with the inverter cooling or P0A93. You can always use a scantool - app that has hybrid control ecu data to see what the inverter temperature sensors are showing.

Now, with the ignition switched ON (dashboard warning lights on) or in READY, does the pump hum or feel like it's vibrating some?

If yes, did you bleed the inverter cooling system? There's a bleeder fitting on the front of the inverter. I take off the little rubber cap. Put a length of small tubing (I like transparent hosel from the bleeder and secure it into the inverter coolant tank. Ready up the car then open the bleeder a turn or two. Coolant and any air should flow out- top up coolant level as needed until air bubbles stop coming out (pump should be quieter). Close the bleeder.

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If that's the case, I'm thinking the system is clogged somewhere. You can unclip the hose from the pump discharge (the tangential nipple, not the central one), or maybe unclip the other end of that hose, where it attaches to the tranny, and pull the end up kind of level with the reservoir. Make sure there's coolant in the reservoir, goose the pump briefly with 12 volts, see if it briskly pumps coolant out that hose. (Try to avoid running the pump without coolant; not good for it.)

If that confirms the pump itself works, then it's a matter of checking the various ins and outs of that coolant path, looking for somewhere coolant won't flow.

 

Welp ... it looks like the pump is fed with coolant from the reservoir (through hose G9226), and pumps it out into hose G9227, over to the MG1 half of the transaxle. And if your test shoots coolant healthily out of hose G9227, then the clog isn't in any of that first part of the path.

So the coolant then passes through the MG1 heat exchanger and back out through the short little hose G9228 to hop over to the MG2 side of the transaxle. After passing through the MG2 heat exchanger, it's into hose G9229 to the left side of the inverter radiator. From the right side of the radiator, hose G9225 takes the coolant back to the inverter itself (so the electronics get the coolant at its coolest, because it just came from the radiator). After passing through the fins inside the inverter, it returns into the reservoir. (There isn't another hose for that; the reservoir has an opening bolted right up against the outlet from the inverter.)

Somewhere in that second paragraph, something is clogged. Now just to find it. Kind of a job for a curious plumber.

 

So, the little short one that just hops from one side of the transaxle to the other?

Funny place to keep a spare bolt.

Probably the prior owner went some time without changing the coolant. When the corrosion inhibitors are used up in the coolant, the aluminum fins in the inverter and transaxle heat exchangers start to oxidize. Aluminum oxide is this funny jellylike stuff when it's in water. I flushed a bunch out of the bottom of my home water heater when it had an aluminum anode rod.

Spread out in a pan and allowed to dry, it then looks like some sort of weird breakfast cereal. Maybe you can pulverize it and use it to make sandpaper.

 

Congrats on the fix- and the persistent methodical testing that found the problem.

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What size bolt was it?

My first guess was that somebody stuck a bolt in the end of some hose to keep it from leaking, for instance when changing the inverter pump. But that didn't really make sense, because one couldn't just "forget that it was in there", as the hose could not be reattached.

That brings up a second scenario - that the bolt came from somewhere inside one of the components which are cooled. So if you can identify the size of the bolt, perhaps somebody here can suggest its original location. You know, in case maybe it should be replaced.

The third scenario is that some idiot dropped it into a component by accident at a factory, and it has been floating around in your car ever since, only now getting stuck in that particular location.

Odd things can be sometimes be found in unexpected places. I thoroughly flushed my home water heater recently and an RFID tag came out.

 

That's just weird.