I posted something similar today on the Prius forum as well.

I have a 2010 Hybrid Highlander that has an EV button on it. However, as we know it only works under certain limited conditions. I have read about the Coastal Tech EV and similar mods for Prius that ground one of the pins (27) on one of the Hybrid ECU connectors (H14) and this seems to work to keep the engine from turning on at initial power-on. I'm interested in trying this as a first step in a plug-in conversion project. However, there is not so much information out there on the Highlander and I have some questions.

-> Can anyone confirm that this mod does in fact keep the ICE from starting when cold? Not like the EV button that is there. Or does the stock EV button just do the same thing as the mod above?

-> The connectors on the Highlander Hybrid ECU are apparently labeled differently as compared to Prius; I am looking at a diagram from Alldata where they are called B1, B2, B3. And then under those is A43 and a couple more unlabeled ones. I guess the A43 connector seems to be in the closest location to the H14 connector on the Prius, but does anyone know for sure which pin is the one to ground?

Thanks for any feedback.

 

Unless your plan is to add additional battery banks to the system I don't think you'll get much from a plug-in Highlander hybrid (grid charging system is not easy/cheap to build properly). Also the battery pack capacity relative to the size/weight of the vehicle is alot smaller than that of the Prius. Not sure on the EV button mod but the folks on Priuschat are likely your best source for info as there are alot of extremely knowledgeable people on there which would certainly be able to answer all your questions about adapting mods to the highlander.