Navigation Input Override (Speed Sensor Bypass)

Yes, it is fortunate for you that I am not a moderator. It is somewhat less fortunate that 4800+ posts seems not to have imparted the ability to stay on topic. But evidently post-count is a substitute for manners these days, so I'll keep to my place from now on.

 

Racheal... with due respect... most topics on PC carry a broad swath with points taken and considered.

4800 posts means I've read much more and learned much more than I've posted.

Enough of the family spat....... we give new folks repect to state their mind... but new folks are usually interested in gleaning from those who are veterans.

There are some very smart people on PC.... both in education as well as common sense.

My hat is off to anyone who can actually make a circuit to bypass the programming and be so humble about it.

Way to go hawkmoon77..... I could never dream to build such a "simple" circuit as you call it.

I guess we all have our areas of expertise.

 

Gotta go with you on this r7. The point of the thread is not WHY Toyota did it but how do we fix it. Going to Toyota and their lawyers is going to get us nadda. They darn sure aren't going to fix it for us.

 

Sorry, when I asked what I thought was a rhetorical question I should have known that we would go off-topic. Anyway, I hope that we can find an override without having a need to blame anyone who might have provided input to Toyota's or Denso's decision process.

Regardless, those decision were made and now some users would like another nav input option -- so that should be the focus of the discussion. It looks like there's a simple hardware bypass, but I hope someone will find a software one.

 

Agree. The point of the thread is how to bypass it. While windstrings may make very valid points, I believe that discussion belongs in the General forum, not in Accessories and Mods, and certainly not in a thread that through 80 posts has been focused on solving the problem, not debating the reason it exists.

 

Thanks for sharing this, hawkmoon. A very similar circuit to what I'm playing with.

A couple of comments and a question (warning: not for those who get bored with technical details ):
- If C1= 22uF, and your R2 = 1K, then a value of R1 = 10K would give you a frequency of about 5.3 Hz - but at a 90% "duty cycle", meaning the signal is high 90% of the time, low 10%.. This probably still will work just fine, since the pulse is so slow from a digital logic standpoint and the NAV can probably respond to it with no problem. But according to the repair manual, the pulse is supposed to be close to a 50% duty cycle.
In my experimenting, the lockout engages at about 6.0 Hz (and you actually need to drop significantly below 6 Hz to get access back again) so I think your 5.3 Hz frequency is darn near perfect! I too am using a potentiometer, but for R2. My values are C1 = 1uF tantalum cap (higher V limit and smaller size), R1 = 1K, and R2 = approx 130K (150K pot). This gives 5.3 Hz and 50% duty cycle.
- I'm going to be triggering the pulse two ways: A timed pulse, about 1 minute long, that will return automatically to normal (lockout) condition without me doing anything (enough time for me to make a few touches and make sure it gets turned off); and a switch/relay circuit similar to yours. I'm using a switch that has a momentary connection one direction, and "hard" switch the other. "(ON)-OFF-ON" in switch jargon.

Now the question:
Can you tell me why are you using an electrolytic cap in series on the output? Did you see this in an example circuit somewhere? (I have not seen this used on a 555 Timer before). What this does is "AC couples" the signal to the NAV, and causes the signal to "float' away from the ground reference. I tried this and watched it on a scope while connected to the NAV, and noticed that the pulse output going into the NAV "shift" from 0-10V (without the cap) up to 4-14V (with the cap). (By the way, a 2V drop from the Vcc voltage is normal for a 555 timer output - that's why the 10V high value..) This "level shift" depends on the "load" that the NAV is putting on the 555 output signal, and whether the logic input is pulled up (to 12V) or down (to ground) internal to the NAV. (I suspect it's pulled up.)

You might want to think about removing that cap - you may not be putting the pulse you think you are into the NAV (because the output is no longer tied to your regulated Vcc.) The circuit still may work just fine (as long as the "low" state doesn't rise too high to not trigger the NAV input), but it's not the same pulse it's supposed to be getting from the wheel. It's shifted upward.

Thanks again for posting your circuit!

(BTW, I've discovered something very cool regarding the auto headlights. See that thread, if anyone's interested.....)

 

Sorry for the stray... Rodjo.. I get pretty wound up sometimes after a 14 hour shift at work...

anyway, I agree a software bypass would be awesome.. but I'm not sure how we would "impregnate" the addition without assistance from the toyota dealer.

Seems we can't even adjust locks, headlamp timeouts or virtually anything anymore without their help when it comes to software.

I'm thinking the hardware solution may actually end up being the easiest and possibly the least detectable if installed discretely.

 

As I understand it the circuit is exploiting a hole in the software. It would then seem that a code change could defeat the circuit, if they were so inclined.

 

Good point and I agree... just not sure how we could introduce that code unless Toyota was in on the deal.

We would have to have a device that could link up to the computer port to do so.. something most of us don't have and it would be cost prohibitive to buy such a device just for software mods.

I just don't know enough about the system to be aware of just "how" to do such a hack or software mod.

I have no problem with hardware mods... as long as when they are removed, it renders everything stock and factory functional again.

I've never removed a mod yet that I've done so even that is a non issue for me.
Even when selling the car, I would think the new buyer would welcome the existing mod... especially since fear of violating some warranty wouldn't even be an issue.

Speaking of that.... its much safer IMO to introduce a hardware mod and be able to defend yourself in a warranty claim as they would have to "prove" your mod affected the failed issue at hand before they could not cover the claim.
On the other hand.. monkeying with the software would be much more of a warranty violation unless the mod was totally undetectable by most prius mechanics.

Based on what I've seen so far, the latter would not be difficult to accomplish!

 

the real question is "will you be offering a bag of parts to allow consumer-assembly of the unit any time soon"

 

Injecting the code is the easy part, it's decrypting and modifying the code that is difficult. The code is part of the DVD that goes into the NAV system, so IF (and yes, that's a big 'if') someone with the appropriate firmware knowledge could decrypt and modify the firmware, installing it would just be a matter of burning a new DVD and sticking it in the head unit. And removing the mod, like for warranty purpose and such, would just be a matter of putting back the original DVD.

 

Soldering and orienting the caps right could be room for error with most of us....

If the package was already assembled ready for plug and play would be better and worth the price IMO.....

I'm just trying to figure out the best or easiest way to get the thing mounted without pulling the whole center console apart....

If thats the "only way".. so be it.

Before with the Gen II, I could tap into the wire that comes out of the DVD player underneath the seat... now the DVD appears to all be in the dash so dismantling may be the only way unless there is a tracer wire that runs underneath the dash that could be accessed without ripping stuff apart.

 

A lawyer that hacks his car. I like it.

 

I have the skill, just not the time. And that includes disassembling the code and the hardware to understand enough to make the mods necessary. Years ago, I modified the software on my AVIC-N1. Unfortunately, life is a bit busier now-a-days.

 

It is amazing what folks can do. (Especially when an 'expert' can tell them why it won't work...)


I manage a young design team and we had a project that other teams said was 'impossible' or 'too difficult'. My team got it done while the other teams were still making excuses...

hawkmoon77 , I admire your willingness to 'jump in' and just do.

 

LOL! Well there are good ones too.. otherwise we would all really be in trouble.

Incidentally.. I"m in the medical field and what simply makes one person mad can cause severe burns on another.

Good example is a babys skin or a womans skin or even an uncovered leg "wearing a dress" verses spilling on clothes or jeans first.
Another factor is what they did with the burn afterwards.
I got 600 degree hot tar burns on my arm while roofing.. part of it I peeled off immediately afterwards until the skin started coming of with it.
All the areas I "did not peel" ended up with 3rd degree burns which needed skin grafts, while the areas I did peel is barely noticeable now "without skin grafts".
Difference being heat was released when I peeled the tar off verses not and less damage occured.

I agree, allot of coffee is too hot to drink for my taste... but I think we all know coffee is hot unless ice cubes are in it.


The whole point I was making, I'm sure you can identify with if your a lawyer.
Toyota is afraid to let us access what we have paid for while driving for fear someone will blame them for recklessly building a product thats dangerous to drivers.
You also know, law suits follow the money..... which makes Toyota a big target.

Getting back on topic, we as customers should have the liberty to put bicycle tires on our cars for max gas mileage if we want... regardless of the dangers involved, especially if we did the mod ourselves and Toyota is not responsible for our actions.

I guess thats the bottom line... we and we alone should be responsible for our actions and Toyota should be responsible for their actions..... the lines seem to get blurred in court.