Navigation Input Override (Speed Sensor Bypass)

[hawkmoon77]

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.

[ggood]

Where did you mount the switch? Pictures soon? I'm a dummy, but I recall people using a momentary switch on the gen 2 mod. Is that also an option, and are there pros or cons?

[hawkmoon77]

Originally Posted by ggood

Where did you mount the switch? Pictures soon? I'm a dummy, but I recall people using a momentary switch on the gen 2 mod. Is that also an option, and are there pros or cons?

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.

[hawkmoon77]

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?

[rachaelseven]

Seems to me you'd still need an of/off switch. It's my understanding that the NAV system uses the speed input to increase the accuracy of it's position (like dead reckoning, in formal terms), so with the NAV system receiving a constant 5mph input, whatever voltage that might be, there would be an accumulating error between the SAT input and the speed input, which is bound to make something unpleasant happen. It would be nice not to have the one minute limit and lose the address when you were half done inputing it, so maybe switching between the regulated input and the real input would provide a good solution?

On the other hand, the time limit you're encountering might well be due to the accumulation of error between the SAT and speed sensor (at zero when disconected) and tricking it into a 5mph speed sensor input might only gain you a few extra seconds of function before the error accumulates to the same maximum allowable value. It could also be that when the car re-checks the satellite data periodically, it calculates it's speed from the position data and decides you're moving whether or not it's getting speed input. Would be interesting to see if the NAV input locks out when you're riding on a flatbed...

[ggood]

FWIW, prior install articles and threads for gen II nav defeat switch:

Gen 2 -

Prius Speed Wire

2006 navigation- override
[ KB ] How to Install a Navigation System Defeat Switch

How To: Nav System Sensor Defeat - Use Nav while driving

Gen 1 -

Prius NAV Mod

The original how to article from Dr. Fusco has disappeared, unless the top one is it. There are a lot of broken threads to the original gen II nav override switch. It appears his method may have also involved a rocker switch, but I thought I remembered people trying both timer switches and momentary switches. One of the old timers who knows what they are talking about should speak up, like Doc Fusco, who created a how to article based on info he got from someone else, and his own install experience.

[94Aspy]

It seems like the voltage emulator would be worth the extra components... given the convenience that it would add. Having a short window of time to make Nav adjustments could be frustrating for the passenger (or driver, lets not kid ourselves here, folks).

Here is my thought on the general topic: the Prius seems to be an automobile that has become the standard for next-generation technology in cars. That said, it also seems like it attracks many tech-saavy owners. I would think that this would mean someone would figure out how to hack the Nav system via the DVD update system and just disable the Nav overide... without the need for hardware additions.

Is the programing in these things that hard to reverse engineer?

[hawkmoon77]

Originally Posted by 94Aspy

Is the programing in these things that hard to reverse engineer?

For me, yes.

[brosnan]

Originally Posted by hawkmoon77

UPDATE:

... or should I install a simple voltage regulator to tell the NAV system that I am moving at < 5mph?

...

Thoughts?

On the 2004, I found that substituting the speed signal with one equivalent to ~3mph allowed access while moving without triggering the secondary lockout. In that case the speed signal was a digital one and 4.7HZ from a TLC555 timer did the trick:
http://www.wb5mrn.com/prius/schemati...to_defeat5.pdf

If they've moved to an analog speed signal in the 2010, that would require a different technique, but perhaps the general concept would still work and make for a more convenient passenger "lockout override" switch (no need for repeated presses) like I had for the '04.

[hawkmoon77]

Originally Posted by brosnan

On the 2004, I found that substituting the speed signal with one equivalent to ~3mph allowed access while moving without triggering the secondary lockout. In that case the speed signal was a digital one and 4.7HZ from a TLC555 timer did the trick:
http://www.wb5mrn.com/prius/schemati...to_defeat5.pdf

If they've moved to an analog speed signal in the 2010, that would require a different technique, but perhaps the general concept would still work and make for a more convenient passenger "lockout override" switch (no need for repeated presses) like I had for the '04.

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.