Prius 2001 heat Gauge

Sorry, I missed in your earlier post where you mentioned being overseas with no access to a proper scanner.

It's very likely that the temperature light and the P3120 are telling you about the same problem, so when you fix the problem you'll be done with them both. Not having the INF codes just means having to do more of the diagnosis the old fashioned way. You know something is getting hot. Probably not the engine, because there was no engine code for overheat, the coolant doesn't feel hot, and the engine thermostat wasn't the fix.

So it's probably safe to guess that if you could read the P3120 INF codes, you'd find one (or more) of the ones having to do with transaxle/inverter overheating, and going on that guess it would certainly make sense to check the inverter coolant circulation. The pump should be running any time the key is ON, and whenever the pump is running, you should be able to see about a 2 cm 'waterfall' inside the small coolant reservoir that is about centered under the hood, between the engine and the inverter housing. Do you see that?

-Chap

 

Try here.

-Chap