Hybrid System Overheat message - but no codes

For starters, stay away from Toyota Stealerships... They are warranty specialist and have zero practical experience at keeping a decade old car running for lowest cost possible. Their only objective for a car as old as yours is error codes that make the cost of repair the same as $elling you a new car with "generous" financing package.

What you need to do is get an ODB2 reader like this: Panlong OBD2 Scanner Bluetooth OBDII Diagnostic Tool Car Code Reader Turn Off... | eBay and then use an app like Car Scanner (ELM) app on your phone to monitor engine coolant temperature.

I suspect the problem you're having is the thermostat that opens the coolant circulation through the engine is a little slow to respond once engine reaches the right temperature. By monitoring the coolant temperature with your phone you can confirm that.

Years from now, when you change the coolant, you can resolve this by replacing the thermostat. In the meantime, just monitor to make sure it doesn't get worse.

 

Isn't this due to inverter system not cooling. Keep driving see if HV battery charging is walked back by the internal systems ?

 

Your engine water pump is going bad. This will first show up when you are driving on the highway (high speed). You need to replace the water pump ASAP! My recommendation is only to use an OEM pump. Do NOT drive your car at highway speeds until the pump is replaced. Every time you overheat the engine, the higher the probability that it will lead to a head gasket failure.

PS, since you are at 99k miles, you should have the engine coolant replaced when the water pump is replaced. Toyota recommends that it be replaced at 100k miles.

 

FYI, the engine water pump can go bad without triggering a trouble code. There are many different threads in the Gen 3 forum where the pump has gone bad without setting a code. Do a search if you want to do more reading. Without the trouble code, most dealers are clueless about what the problem is.

Keep a close watch on the level of the coolant in the plastic reservoir on the passengers side of the engine bay. Add red Asian coolant if it drops below the minimum level line.

Get a quote from the dealership and a couple of independent shops to replace the water pump and coolant.

 

Man that's a 45-minute job with Walmart tools no kidding seriously Just move the snorkel out of the way and you got plenty of room to work and just pull the impeller and look for all the cracking and flaking If that's what you got buying impeller and drop it in there and keep getting it usually it's the impeller cracking splitting swelling that's causing it to be able to not turn consistently move water and cool your car It's not that the pump is bad the impeller which is like part of the mag drive system is covered in plastic and that stuff is cracked and swollen and it's keeping the thing from spinning well drop a new impeller in there and you're off and running to the races maybe run a little less than a 50/50 mix of antifreeze where you can might help with the plastic splitting