Failed Cruise Control install

I bought a Cruise Control unit for my Japanese import 2006 Prius, and got a Toyota dealer here to install it (even though it sounds easy-ish to do, I wouldn't trust myself to do that, haha). They plugged it in to the socket on the side of the steering wheel, but nothing happens when you press the buttons or such.

They plugged the switch into their tester unit, and its working fine. It delivers the right instructions through the cable. But nothing happens when it's in my car.

They said there's no marker on the dashboard for it either, so they didn't see how it was going to work in the first place. What they wrote on the paper was "suspect because the vehicle ECU doesn't have provision."

I wonder, did I miss something? Or maybe it's not a mod possible on Japanese Prius?

I asked them to leave the switch in there for now, as it would cost more to have them remove it again. Thankfully they only charged $30 for putting it in and trying it.

 

Thanks!

I don't have the stop light switch (8434020060) or the steering wheel right lower cover (4518647010C0). This is what I purchased:

2006 Toyota Prius Cruise Control Switch 18A174 OEM 04 05 06 07 08 09 | eBay

I take it that includes the cable to connect the switch (8463348020) but thought I better double check

Most of the instructions there look easy enough, but I don't have anything to measure torque and measuring a distance of between 0.5 and 2.4mm in such a space sounds like it'd be tricky. But is getting the torque right vital?

Thanks again for your help

 

Agreed, I'll ask the dealer to install it. Better than risking it.

Thanks, I'll place an order for those parts now.