Electric Motors not running intermittently

Yes, check battery cooling duct and fan. Can you read battery temperature when this occurs?

 

was it hot out? there's a battery protection mode until the battery comes down to a certain temp.

how many miles on her? the older and weaker the battery, the earlier and more often it may enter this mode

 

The Prius does sometimes randomly do this as it does a cycle on the battery. This happens in Gen-3 and up. As the battery gets weaker and weaker over time, like yours being 8 years old now, it is more and more noticeable.

Now this can also be a sign of the car protecting itself. This can be because the battery is too hot or inverter is too hot. On a Gen-2 and Gen-3, first thing I'd check is for turbulence in the inverter coolant pump reservoir. It is a pump that can die and it's only function is to run the cooling loop that is just for the inverter. When the pump dies, the car works just fine, but the inverter gets hot. So the longer you drive, the hotter it gets until eventually, it does as you describe. Eventually it will just refuse to move as you encroach temperature error territory from temperature warning territory. On the Gen-2 the pump has been part of a recall. I don't believe so on the Gen-3. But it is still a weak point.

Also on the Gen-3's the inverter itself is a weak point, whereas it is not on the Gen-2. The Gen-2 is built like a tank. The Gen-3 is built to save money. There is also a recall out for the inverter. A partially failed inverter could cause self heating and then the symptoms you describe.

If the battery is hot, this is easy to tell. The fan will come on in the back. Turn down the radio and roll up the windows, and listen to the little HV battery fan. If it is loud, your battery is hot.

 

Since you have a dog, with LONG hair, I suggest the following:
Hybrid Battery Fan Filter: $12.78
Part Number: G92DH-47010

Also install this foam filter with it, you cut it to fit:
Lowe’s Air Filter
Frost King (common 15x24) Washable Filter
Item # 78359 Model # F1524 $2.00

This attaches to the right rear air inlet, next to the seat back.
Easy to remove and wash with water.
I have to dogs, and have other dogs I train and transport, and this catches it all.

 

It can also be the 12v battery is not able to retain operating voltage charge so ICE is staying on to continuously or longer charge the 12v because it’s deteriorating,

 

The engine running isn't directly needed to charge the 12 volt battery though.

Power to charge the 12 volt battery comes from the DC/DC converter and from the high voltage system in the car (so, from the traction battery, whenever the engine isn't running). The engine will, of course, cycle and run as needed to keep the traction battery charge within limits. The 12 volt battery is getting a constant charge whether the engine is running or not.

 

I would recommend buying a scanguage or an OBDII plug and using an app like hybrid assistant to check the state of the car.
That, or go to a Toyota workshop and have them diagnose it.

 

If your 12v is more than 4 years old, change it. Also your electric motors always are working if you're moving. Your gas engine is just staying on. A hybrid Toyota can't move without the electric motors

 

Well, it's been over a week. Everything still OK? The HV interlock error was because you didn't have the interlock properly seated. You insert the interlock, fold down the handle, and then slide the handle toward the pivot hinge. This locks it in place and also closes a pair of contacts that tell the ECU that the interlock is in place.

 

I've cleaned that fan a couple of times, without pulling out the interlock switch. I'm still standing.

 

Right. No reason to pull the interlock just to unplug a 12V fan motor. Totally different system.

 

I found too, you can completely clean the fan without removal; just pull off the ducts connecting to it, any covers.