Yep, this is probably it. Even without pushing the EV button, it would normally go to battery mode during low speed driving... not this afternoon.That said, there is a list of things that might prevent its use. That list is published in the owner's manual. One of those things is the internal temp of the inverter/converter system and battery.
It happens to me too. Specially when I'm doing long downhill the battery gets fully charged and at some point it will turn off the automatic EV mode and then starts the engine. At that point no EV mode is available manual (via button) nor automatic. It probably needs to cool down some parts of the hybrid system to prevent damage.Does anyone get this when trying to switch to EV mode via button? Seems today with 100+ temp F, I am unable to switch to it at the end of my commute - despite having full hybrid battery.