ICE Won't Turn Off

I see this question quite a bit, but not with a very satisfactory answer. So I'll just put this here in case someone looks it up some day.

If there are no maintenance lights illuminated, the number one reason I see for the ICE running excessively, is to keep the traction battery from exercising.

Toyota hybrids have a traction battery heat protection strategy that limits how much the battery is exercised. When the traction battery gets to a certain temperature, the ICE will progressively run more and more. Depending on how hot the battery gets. It will go to the point where the ICE will not turn off at all, running while sitting at stop lights, etc.

While the battery fans can fail, it's pretty rare. Every time I've seen this, it's something on the back seat floor, blocking the duct, or the screen on the front of the fan is covered with debris/lint. The fan is nothing but a "squirrel cage," and while it can move a lot of air, it doesn't have a lot of force, so airflow drops substantially with any obstruction.

I've attached a picture of the fan in place under the seat, and a picture of it removed, screen showing. This screen can be vacuumed by just removing the plastic cover under the seat. No need to remove the fan.

Hope this helps someone.