Prius "headlight" EV mode mod
Another elegant way to install EV Mode is to use the headlight flasher. This is an even easier installation requiring no special circuit and only one wire. To do the installation leave the bottom cover of the steering column off when you retrieve the connector pins. Now, put one of the connector pins on both ends of a strand of wire. Plug one end into the ECU just as with the standard EV button. Thread the wire behind the dash but then pull it up along the steering column. Pull out the purple wire from the flasher plug and insert your EV wire into the now open slot. (Properly removing the purple wire will require splitting the two rows of pins into their two separate connectors (which are snapped together in a stack). A thin sharp knife between the two pops them apart quite easily, making it possible to release the purple wire properly but pressing on the same spot you use to release the spare pins. Just yanking it out otherwise is not a good idea. It also makes it easy to ensure your replacement is inserted properly, as you can see the pins end-to-end.) There is no need for an additional ground as the flasher is already grounded. Once reassembled you have a reversible and invisible EV mode. Your headlights will still flash when the headlight stem is pulled toward you while the headlights are on. You just won't be able to flash the lights when your headlights are turned off. EV is engaged or disengaged by pulling the headlight stem toward you.