The first way that comes to mind is push the power button. Every time u start your hybird it goes through an oxygen sensor warm-up procedure for a minute or two.

Another way is to just step on the gas while in park will start the ICE.

Just a couple way of starting but there's an emissions test procedure that will also start ICE in two different RPM modes. I forget where I saw that procedure but it was in states where vehicles require periodic testing. Max