WTB Gen 2 Prius EV Mode Button Wiring Harness

It will only work for maybe a half mile at 20 mph if you are lucky.

 

You might try Coastal for their kit. The web ordering does not work but maybe you can call.

https://www.coastaletech.com/electric_only_mode.htm

Or you can diy using any switch but its some work. See pdf

 

This would be helpful for my early morning departures from home while the family is sleeping. So the switch while on tells the HV ECU to not turn on the ICE? Basically?

 

Yes. Although the engine will engage if the hv battery gets too low or you wait too long. Its a momentary pushbutton.

 

I remember doing this mod following the instructions in the PDF from Dr. Fusco above years ago when I had my Gen 2. I am not a mechanic or electrical engineer, but consider myself up fairly handy. The job was a bit tedious and time consuming (and a bit nervous any time you are plugging something into an ECU since this is an expensive computer…), but easy to follow the steps with some patience and worked as expected (big exhale at the end…).

Basically, if you press the new EV button, it will suppress the engine from starting and remain in “EV” mode for a shot distance, even though the North American Prius did not officially have this feature. Note that doing this will NOT light up on the dash to indicate EV, despite it appearing there to be a light for it, visible in the right sunlight. Not sure if anyone ever succeeded in wiring that light, assuming there is even a bulb there.

The only clue feedback or clue that you will get when engaging EV is the display will switch to the Energy Monitor screen, if you were not already on it.

It is a nice party trick (particularly since this was before the noisemaker and the car will move completely silently ), but since all energy comes from gas anyway, it will not save any money on fuel due to energy conversion losses. It does change the characteristics of the throttle though - you can accelerate a little more briskly (and to a higher speed) before the engine kicks in compared to the stock hybrid operation.

Good luck if you decide to pursue this mod!

 

Sarge,
Thanks for the help. I did complete the mod but no EV light on the dash, or a beep. Thanks for letting be know I won’t see one. I’ll try to have the display on the HVAC screen to watch it switch to the drivetrain Battery screen. I may have put too much solder on the pin which prevents it from being inserted deep enough into the connector and it is not making contact. I will have to double check my work. Not sure where the signal for EV mode would come from. But rigging an LED would be easy enough once the correct pins were located. Maybe from EE schematics from a Japanese or EU model. thanks for the info.

 

You are most welcome. Yes, it is strange there is no other indication when it is engaged, I remember thinking the same when I wired it up, then held my breath and pushed the power button and then pressed my new EV button. I was initially disappointed thinking something wasn’t right and it didn’t work, until after a minute or two I realized it did, and switching to the Energy Monitor was the only hint. FYI, mine was a 2006, the behavior could also vary from one year to the next.

Cheers.