That harness is exactly like the Supra ECM extensions. Note the black shrink tubing on the end that the car's harness plugs in - the connector is the same one used on the pc board, they've just attached wires to the pins that would normally be soldered on the board and put shrink wrap over them. The other connector is commercially available in quantities (or possibly engineering quantities of ~5 or so with pins included) from the manufacturer (most likely Sumitomo) and the wires are just anything they happen to have on hand. Building this piece is a no-brainer for someone with harness building experience and could be almost free if you request engineering samples.

 

You wouldn't want to disable this because it is also enables the smooth scrolling. Every few seconds (or five or ten) the navigation unit queries its built-in GPS to determine your exact location. Between GPS measurements the navigation is using steering and the speed input to smoothly scroll your position the same way it would use these inputs to keep you on course should GPS reception become less reliable. This is why there is an implementation of the nav hack where a switch is placed inline the speed wire so that you can turn off the speed indication when you want to input a destination while moving. If you just cut the wire completely, navigation scrolling becomes jumpy.

I've noticed that it's pretty easy to confuse the navigation unit by not giving it a good steering direction indication such as when getting off a highway where you just have to turn the wheel a little to take an exit ramp. It seems the navigation doesn't get the message that you've turned off the highway and will keep your current position indicator moving along the highway as you drive parallel to the highway on the ramp or a frontage/service road. It's not until you make a sharp turn onto another street that it finally picks up where you are and jumps your indicator from off the highway to your actually location.

That's one of the few bugs I've found in the navigation unit. That and a little bug in the POI display (there's a misspelling where it says "diaplaying POI icons") and when it returns from the POI screen it doesn't remember that you were on dual map mode and dumps you back into single map mode.

I've also found that there are some undocumented commands not listed in the manual and navigation voice help. One is "lane guidance" which I'm not sure what it is. I tried it and it responded with "activating lane guidance mode" or something like that, but it really didn't change anything. I also tried "next folder" while playing an MP3 CD, and it just said "command not available on this screen" while I was on the audio screen. Perhaps it thought I said something else.

I did see a graphic while under guidance that showed the highway I was on I-95 with a picture of the number of lanes which I thought was pretty amazing that it knew the exact number of lanes and perfectly accounted for on and off ramp lane drops that I happened to be passing.