Heating up of Toyota Prius Wagon third generation

Dear Toyota users,

I have a quick question. My Toyota Prius Wagon, third generation, year 2013, has recently been showing an overheating warning on the dashboard. After a few instances, the check engine light also appears, which causes the car's speed to be limited.

In reality, the car drives just in gears 1 and 2. Even on the highway, I can't accelerate anymore.

I took the car to the garage and we checked the fault codes. The error code P0A93 came up, indicating a possible issue with the inverter cooling pump. I ordered and replaced the part, but the problem still persists.

The coolant has also been replaced.

I’ve noticed that when the car heats up, there’s no visible coolant circulation in the reservoir.

Has anyone experienced this issue before? What was the solution in your case?

 

Thank you very much for your response and feedback.

I would like to kindly ask what exactly you mean by the head gasket. In the inverter and cooling system circuit, there is a water pump, an inverter, a reservoir, and several hoses.

However, I do not see any gaskets there.

If you could assist me further and clarify what exactly you mean by the head gasket, I would greatly appreciate it.

Thank you again for your time and support.

 

I will follow your steps. However, I think I will first take the car to the garage and put it on the lift. Then I will check whether there is any voltage at the connector going to the heat pump.

After that, I plan to drain the coolant from underneath the car — not from the top. Then, I will blow compressed air through the entire coolant circuit to clean it out.

Once everything is flushed, I will close the system, refill it with coolant, and bleed it. Then I will observe what results this brings.

If there is no voltage at the pump connector, it likely means that a relay — the one responsible for sending power to the pump — is defective. It could also be that the sensor inside the inverter is not sending a signal to activate the heat pump.

I will keep you informed. Thank you again for your kind support and for thinking along with me so far.

 

169441 miles/ 272698 km

 

I just returned from the garage. I placed the car on the lift and had the coolant replaced.

Then I measured the voltage at the connector attached to the inverter heat pump. The electrician confirmed that there is power present.

The pump has four pins: a positive and a negative. The other two pins are likely intended for signals from a sensor to switch the pump on and off.

However, I do not know where these signals come from, as I do not have access to a specific wiring diagram.

Despite replacing the coolant and checking the connector, the pump still does not operate.

I drove the car for a short while afterward, but unfortunately, the issue remains unchanged.‍♂️

 

Thank you very much for your response and for thinking along with me about the issue. In the meantime, I've been busy googling and researching. Through ChatGPT, I found a wiring diagram. I suspect the problem lies with the ECU — these are the pins that control the pump. I'm going to take the car to a garage to have this further investigated.

I live in the Netherlands, and the dealer here was extremely expensive. That's why I take my car to an independent garage, although I often have to assist and explain things myself. What exactly should they do?

I was charged around 560 euros for 2.5 liters of coolant and cleaning the cooling system. The hourly labor rate is 160 euros. That’s why I decided to investigate the issue myself and bring the car to a garage so I can tell them exactly what needs to be done.

Below, I’ve included a link to an expert who clearly explains how to measure where the problem might be.

Once again, thank you very much for your help. I’ll have my car examined and will keep you updated. Thanks again!

 

Why do I think the ECU is the problem? Because one of the ECU’s functions is to control the pump and manage the discharge of the hybrid battery. The issue started about five months ago. When I get out of the car and try to close the door, I receive an electric shock. This happens every time I attempt to shut the door. I suspect the discharge is occurring through me. I believe the ECU is not properly handling or processing the discharge process. That’s when the issues began, in my opinion. Based on my research, managing the discharge is a crucial function of the ECU.

 

I have an appointment at a garage this coming Wednesday. There, I will measure all the wire pairs using an oscilloscope to check the frequencies and their corresponding standards. I will let you know the outcome afterwards. In any case, thank you very much for your feedback.