A NAV Bypass Proposal for the wiring Pros....

I realize that this topic has been rundown, and there are some very extensive DIY's. I just downloaded the TIS Wiring diagrams for my 2012 Model 5.
In the past there was the option to "switch" off the SPD signal temporarily to allow the use of the "locked out" screens. I have had a couple Lexus IS250s in the past and over at the Lexus forums, I was able to figure out a way to permanently bypass the spd signal from the multi-display and continue the signal directly to the nav, thereby eliminating the need for a switch and also there is no lapse or degradation of the cars tracking on the GPS screen.
I am wondering for the Pro's out there that have had their Headunits out, are the wires that go from the multidisplay to the NAV unit External or internal? Particularly I am looking at the "Violet" wire. That particular wire comes from the ECU, on to the NAV, to the amp (for ASL) then finally to the Multidisplay.
Essentially, if that wire is external (Like it is on the Lexus) We can intercept the signal from the Multidisplay and send it directly on to the NAV and amp. This way the Multidisplay will always think the car is stationary, and all of the Audio functions and phone functions will work as usual.
I realize this will NOT allow the Locked out NAV functions to work, but all other locked out functions will (ie phobebook etc) . (That's all I want as the voice recognition works really well for the nav)
Sorry for the long winded post. I hope this makes sense to all of you!

 

Thanks for that! Close, but not quite. I do not want to interrupt the signal to the MFD via a switch, I want to the MFD to never get a speed signal, but also keep the speed signal working on the NAV.
My real question is: Are the NAV and MFG the same physical device, or does the speed signal go into them separately.
(I cannot tell from the wiring diagram)

 

....Ok...I took apart my Dash tonight. According to the EWD, the speed wire goes from (essentially) the ECU to the MFD, the on to the NAV then to the "Extension Module" My biggest curiosity was the Extension Module and what exactly it is (hoping that it was Phonebook and Bluetooth etc).
It Turns out it is Made by Harmon and it is in fact the Entune, bluetooth etc controller!
Also it has its own speed sensor wire coming from the NAV unit! I was thinking GREAT! This is what I need. Cut off the speed sensor to the Extension Module, and I'm all set! I cut it.
Sure enough all phonebook and ipod functions were working as if the car was stationary. Navigation was working normally. No glitching etc.
The ONLY FATAL drawback....the car threw a "Hybrid System" problem.
I can only attribute that error to the CAN. The Expansion Module must have reported back to the ECU that it was not getting any signal from the spd sensor, so the ECU threw a code.
I reconnected the wire, restarted the car 5 times. The code went away.

Back to square one...

Can anyone think of a way to do this without a switch ? Again, not for Navigation functions, but only for Phonebook/iPod.

 

Sorry for the Delay! Yes, the Entune module is called the "expansion module" in the EWD. It appears that that particular unit handles all the entune functions. (I could be wrong) I was pretty scared when i go the Hybrid System code on my 2 week old car, so I quickly threw it back together w/o a photo. Sorry!

 

I'll monitor that thread, but if you do end up going, then I'd like to meet you there! Definetly bring a NAV Bypass setup for me. I'll bring the necessary tools to pull it apart as well, so you can see the Entune module and verify my findings.
....let me know about the March Meeting...