P1121 then p1116

No, it isn't.

The Prius Gen 2 manual, unlike the internet, says P1150 is a coolant path clog of the coolant heat storage (CHS) system.

This system uses an electric pump to supply hot coolant stored in the coolant heat storage (CHS) tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned gas that is discharged while the engine is started. Before the engine starts, the ECM operates the electric water pump to direct the hot coolant in the CHS tank into the engine, in order to heat the cylinder head (this process is called "preheat mode"). The duration of the operation of the electric water pump is variable, depending on the temperature of the cylinder head. During normal operation of the engine, the water valve opens the passage between the cylinder head and the heater and closes the passage between the cylinder head and the tank. During the preheat mode in which the cylinder head is heated, the water valve opens the passage between the tank and the cylinder head, in order to allow the coolant to flow from the tank to the cylinder head. At this time, in order to warm up the intake port quickly before the engine is started, the coolant flows in the reverse direction.

This system consists of the CHS tank, CHS water pump, CHS tank outlet temperature sensor, water valve, and a soak timer that is built in the ECM.

If the following conditions are met the ECM will set the P1150 DTC:

• A change in CHS tank outlet temperature and engine coolant temperature after water pump is ON during preheat mode: below 2°C (3.6°F)
• A change in CHS tank outlet temperature as the water valve is opened to the tank, on a warm engine: below 3°C (5.4°F)

Possible problem areas:

• CHS tank outlet temperature sensor
• The water valve (coolant flow control valve)
• Cooling system (clogging)
• ECM

 

You can use your scantool to monitor data for the CHS system.

For the first (cold) start of the day, power on the car to ignition ON (foot off the brake, ie not READY). Turn off the HVAC system. Connect your scantool and go into ECM data.

You want to look at and graph ECT (engine coolant temperature), tank outlet water temp (CHS temperature), water valve position (3-way coolant control valve), & RPM.

Now foot on brake and go READY. You should hear the CHS pump run for around 5 seconds before the ICE starts.

Here's the data from a known good car.
Note how the ECT and CHS temps both go up before the ICE starts.

If your pump runs but temps don't change, I would double check hose routing on the coolant valve.


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That's why I suggest double checking the hose routing at the coolant valve. Look at the diagram - you can see the top two hoses at the valve. One goes to the ICE, the other goes to the heater. If those are swapped, then hot coolant doesn't directly go to the ICE and the ECT won't increase as expected, which would set a code.

I assume since the CHS temp sensor is on the bottom of the tank, that hot coolant leaves from the bottom and is pumped through the coolant valve to the engine and/or the heater.

 

That sounds like B-S speak for "they replaced the obvious parts because they could, and when that didn't fix it they actually checked something and found the fault". They certainly weren't going to remove any parts that they installed. There's no way that something stuck inside the CHS will "short out" the valve and temperature sensor.

CHS resistance chart shows something around 2k ohms at around 70*F

Not sure how that foam piece would have gotten into - well - anything. It's too big to fit into most hoses without being forced in (the heater/CHS hoses are around 5/8" - 16mm inside diameter). Radiator hoses are bigger but that foam would have ended up in the radiator or the thermostat.

That foam piece looks like the bit that's used to seal airleaks around a heater core pipe at the firewall (or an A/C pipe, or a wiper pivot). If that foam was the culprit, I might expect it to be "smushed" like it had been stuck inside a small passage for a long time. Hmmm, smells like more B-S to me (but that's just my opinion)

 

Monitor data as suggested in post 5.

Autel should also have bidirectional controls. You can command the CHS pump on, move the 3-way valve, see if all that works.

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