Nominal / Max values for sensors

700 lbs sounds similar to carrying 4 passengers?

 

I assume you mean max values for sensed temperatures.
The sensors and their temperatures are not what's at risk.

What component and coolant temperatures are you seeing?

 

I would not worry about it unless you see a hybrid code. At that point you could trend that particular point.

 

You have an opportunity to run some tests that I have been wanting to do but have not had a chance to do yet. Test to see if taking the engine cover off will lower the engine coolant temp in any way.

I ran up a steep mountain at 70+mph and my max temp was around 192 degrees. I wanted to test going up the mountain again at same speed but with engine cover off to see if temp lowers in any way. My only concern is if the hood get so hot that the paint/clear coat can get damaged from the excess heat. So there might be unknown side effects involved.

 

Speeding up a steep mountain in a Prius is not recommended due to stress to the engine

This was mainly to monitor the temps as well as performance of the k&n filter. My car had no trouble maintaining the speed, but the temp was what I wanted to monitor. So far please with my k&n filter. Once I do my next oil change I will switch back to OEM stock engine air filters to see the difference in performance as well as the quality of the oil being changed.

 

What coolant temps are you getting? I'm reading that anything above 240 is danger territory. Because that is boiling territory and the sensors may not be able to read the true temp. I'm surprised my max reading is nothing close to that.

 

The Repair Manual, available by subscription to techinfo.toyota.com, gives some reference values in the Data List/Active Test pages of the SFI System and Hybrid Control System sections.

For example, for “Coolant Temp,” the “Normal Condition” is listed as “75 to 100°C (167 to 212°F): After warming up.” For “Inverter Coolant Water Temperature,” Toyota writes, “System operating normally: Controlled at 65°C (149°F) or less.” There are some other values, all “While driving at an ambient temperature of 25°C (77°F)”:

• Inverter Temp-(MG1) and Inverter Temp-(MG2): 15°C (59°F) to 110°C (230°F)
• Motor Temp No2: 25°C (77°F) to 100°C (212°F)
• Motor Temp No1: 25°C (77°F) to 90°C (194°F)
• DC/DC Cnv Temp (Upper): 15°C (59°F) to 110°C (230°F)
• DC/DC Cnv Temp (Lower): 15°C (59°F) to 121°C (250°F)

The thresholds for changes in system behavior or diagnostic trouble codes (DTCs), however, are generally not disclosed. For example, for DTC P0A78-284, Toyota writes, “If the motor inverter overheats, it will transmit an inverter fail signal to the MG ECU,” but under “Typical Malfunction Thresholds,” only “TMC's intellectual property” is shown, meaning the temperature limit is a trade secret of Toyota Motor Corporation.

Because of this, I think @rjparker's advice is reasonable—you’ll need to rely on the car to monitor itself. If a DTC is stored, you may need the Repair Manual to find out why, since the fact that a DTC is related to temperature isn’t always expressed in the fortune-cookie names (@ChapmanF's term) shown by diagnostic tools. P0A78-284, for example, is one of twelve codes called “Drive Motor ‘A’ Inverter Performance”; only the detection condition and monitor description (from which I quoted above) reveal the actual cause.