After scouring the Speed Sensor Defeat Update thread and doing various other Google searches, I still couldn't find the information on how to build the circuit to defeat the BT speed sensor via the steering wheel's Off-Hook button. The link that was given by Brosnan appears to be broken. If anyone has this info tucked away somewhere, I'd appreciate it very much.
Found it. (Actually, I found Brosnan, who reposted it in the original thread). I'm adding the link here so that folks who come later might find the diagram quicker by not having to wade through that entire thread. http://www.wb5mrn.com/prius/bt_only_schematic.jpg Next question: would someone versed in electronics be interested in or willing to make these for sale?
I just finished installing Mike Brosnans solution today. It works fantastic and is a fairly easy install as long as you are good at soldering. Check out my pictures in my post here: http://priuschat.com/forums/audio-electronics/394-speed-sensor-defeat-update-13.html#post668647 I also posted a picture earlier in the thread of my prototype on a breadboard. If you have questions, let me know. If you post in that thread, Mike has been able to help me a couple of times.
It's very interesting, but since I don't need to use the keyboard that often, I'll stick with cutting the speed sensor wire and installing a switch.
I'm pretty sure that it will work on all Gen II Prius. An easy way to verify before cutting wires would be to cut some insulation off of the wire coming from the AU-2 switch (Pin 5b-2 of the wiring harness behind the vent just right of the stereo) and measure the voltages. You would just have to make sure that the voltages are such that would allow the flip-flop to trigger. If they do happen to be different than those posted by Brosnan, you could theoretically adjust the circuit to compensate using the two potentiometers.
