Navigation Input Override (Speed Sensor Bypass)

I would like to install a switch, that when pressed, would allow the passenger the full and unrestricted ablity to enter info on the NAV screen.

Now that my auto-headlights are finished, I will be working on this mod. I believe I have identified the correct wires. The next part will be designing the circuit to control it. It is more than just disconnecting the speed sensor input. While driving, disconnecting the speed sensor input only releases the input restrictions for about 5 to 15 seconds. A small oscillating relay circuit will be required. The trick is in finding the correct on-off interval rate.

Anyone else interested in this Mod?

 

This would not require the whole dash to be removed as I did when I installed the headlight mod. There are pictures on that thread if you want to see how "deep" into the inside of the dash I went.

This mod would require getting behind the NAV unit, which is held on with four screws and covered with a couple of small trim pieces that are held on with some clips. Not the most challenging mod ever, but it would be more than a plug and play addition.

Do to the relative ease of this mod, it is nothing that I would ever charge for or sell to group members (if that was your idea). I would just post instructions on how I did it for those wanting to learn from my experience.

On a related note, regarding the safety issue: While I could technically wire this up so that it would only work if a passenger were present in their seat, it would overcomplicate the mod. If this is the concern, then the switch can be installed out of the reach of the driver, but within the reach of the front passanger and problem solved. After all, the driver does not need access to the override switch since the intention is for the passanger to have unrestricted input access.

 

You know, It's funny you mentino that... I was just telling a buddy of mine that Toyota actually got the clips right. I've had the same experience with every other car I've worked on, including my 2002 Prius. Something about Toyota's design really works here. There were no stress marks (the colored plastic turning white) on the clips, no damaged cor bent clips, nothing. Everything just popped off when you pulled it in the right way. As for bolts and screws. One screw, and two bolts for the entire dissassembly.

More amazing is that when everything went back, and if you saw the photos, you should have the proper context, the entire reassembly took me maybe 20 to 25 minutes. Everything snapped back in as tightly as it came out. I was very impresed with the design.

As for this mod, I will be working on it this weekend. and will post more on Monday.

 

This mod is finished and was very easy.

Yes, it works for audio and phone as well.

Here's how it works:

A simple switch either connects or disconnect the speed input wire to the NAV system. There are no other electronics or anything.

The button is normally "on." When you click the button "off" my passanger has full access to the NAV/Audio/Phone input screens. However, do to the way the NAV system works (where it periodically checks the GPS data) this only lasts for about one to two minutes or so. If they need access for more than that, they need only turn the switch "on" then "off" again. When they are finished, they would press the switch "on" again to reconnect the speed info to the NAV unit.

Note that while the switch is off, the system is not getting speed input and will not track the location of the car on the map. When the switch is clicked "on" again, and speed input goes tot he NAV again, there is about a 30 to 60 second delay before the NAV updates the current position of the car.

While I suppose there are ways to avoid these quirks, this is the simplest implementatino I could come up with (It does only require one $2 switch). It is also very practical.

 

First off, I am not a mechanic nor am I qualified in any way to perform auto work. Below is not my advice, but rather a detailed history of what I did. Please use caution with this or any modification, and please do not in any way rely on my information, but rather do your own diligence and proceed at your own risk. Ok, with that understood, I'll start the detailed history of what I did...

1. Remove the trim pieces:

a. Remove the cover around the shift lever - I first unclipped the drivers side, closest top the cup holder. This was the hardest part. I used my fingernails, but I suppose an old credit card would have helped. Once i had a grip, I pulled upward to disengage the clips. Then I slid my finger underneath around toward the passenger side and lifted upward to pop it out. I removed the two wire harness on the passanger side (not the one on the drivers side). The unit slips over the shift knob.

b. Removed the cup holder trim - I popped out the cup holder by lifting upward in the area behind the cup holder. Once it was popped out, I worked my way up the passenger side. The trim gets very thin here. I carefully pulled out the thin area, from bottom to top, pulling straight out toward the back of the car (not toward the roof).

c. Removed the NAV trim - I started from bottom to top. Pulled out the clips (back and up) and worked my way up the sides (pulling back and up). The area just above the NAV system get's very thin. Carefully, one at a time, and from left to right, I pulled them out. I just got a good grip and pulled mostly toward the rear of the car, but also slightly up). I disconencted the wire harness by the clock buttons and removed the trim.

2. Remove the NAV unit - There are 4 10mm bolts. I got a ratchet with an extension and removed the bolts. They are not too tight, so I kept that in mind for the re-assembly. When the bolts are removed, the unt is still clipped in. I pulled it straight out of the recess paying attention to the clips. Once I got it out, I removed all of the wiring harnesses (there are a lot). A second person held the unit while I unclipped them to avoid scratching anything. It is heavy.

3. Bypassing the speed input - Now that the disassembly is done, it was time to tap into the wire. The speed input wire is the violet wire in pin 3 of connector L42 (gray). I removed the black tape over the wires going to the harness and I cut the wire midway down (not too close to the connector itself) I attached a long wire to each side of the cut wire. Those wires went to the on/off switch. I taped everything up and re-assmebled everything.

 

I do not know anything about a momentary switch. I would be curious how that worked.

As for the location of my switch, I'd rather not post it. I don't think it is necessary for purposes of my report as there really is nothing complicated to it. Some ideas I had were in the glove compartment, near the passenger footwell, on the side trim panels of the passanger area, on the passanger door trim, by the passanger seat, etc.

 

UPDATE:

I noticed that full system input is available for speeds less than about 5 mph. This got me wondering...

Is a speed input bypass system the best implementation, or should I install a simple voltage regulator to tell the NAV system that I am moving at < 5mph?

The thought it that if it get's constant speed information that it is going <5 mph, perhaps it wouldn't autmoatically turn off every minute or two when the GPS catches up? Thoughts?

I was thinking of wiring a up a heatsinked l7805 voltage regulator, with a properly sized resistor to mimick the correct voltage for speeds <5mph (I'll have to check what that is).

I would be concerned about the dropout voltage of the l7805, but without knowing more about the speed sensor wire's operational characteristics, I can't say for sure. My point is the same though, is mimicking speeds <5mph a better bypass then a simple on/off switch?

Thoughts?

 

For me, yes.

 

Great point, I didn't even think of that. i do not have the equipment to test it out though. I just plugged an analog meter into it. I'll try to borrow a multimeter with a frequency counter on it and check it out. Thanks for the idea.