Speed Sensor Defeat Update

[8AA]

I had thought about having a seat switch under the passengers seat, but then remembered that this switch needs to be reset after about a minute. So if you see a Prius with the passenger bouncing up and down in their seat, don't be concerned, it's probably efusco and his wife.

[8AA]

Fortunately, with brosnan's design this won't be necessary.

(All my points to brosnan for his well thought out design!)

[brosnan]

Have you noticed that the nav speed lockout doesn't kick in
until above about 5mph? Well it turns out we can take advantage
of that and create a defeat switch which gives continuous
access to all the nav features. From what I've read, even
those of you with timers on the speed signal to the nav ECU
have moments of lockout. However, by replacing the
speed signal with a 4 pulse per second signal when the
defeat switch is flipped, we can trick the nav unit into thinking
we are moving about 3 mph.

Luckily the navigation unit firmware interprets this differently
than missing speed signals. For missing speed signals, after you
drive about 1/2 mile, the nav unit starts relying only the GPS
signal. This gives cruder accuracy on the map screen and
locks out some nav features, such as "by address" destination
selection. But when the fake speed signal says you're going
3 mph, the nav firmware trusts that and ignores the GPS mismatch.
You can drive for miles at 70 mph and the map display creeps along
back near where you flipped the switch. And since it thinks you're
moving slowly it allows continuous access to the DEST button choices
and all other features. This keeps up for at least 20 minutes
and 10 miles. Maybe you could even drive cross-country with
the map still showing you poking along back near home!

Then, when your passenger has finished with selections,
just flip the defeat switch back to normal mode (passing the
speed signal to the Nav ECU) and soon the nav unit will figure
out it's way off and update based on GPS (although you may need
to drive above 5 mph for a while before that happens).

So far I've done this only with a 0-5V pulse generator. It should also
work with a TLC555 (R/S 276-1718) circuit I've sketched up.
When I've built and tested it I'll post the schematic here.

No real progress yet on the fully automatic version. The phone
and map switches in the steering wheel probably are used in
parallel resistor combinations like the "+,- MODE" buttons
shown in the Prius overall wiring diagram. That would make
them tough to detect. And the DEST, MAP,... buttons in the
MultiDisplay look like they'll be hard to access. If anyone has
helpful hints on these issues, please pass them on.
And thanks for the points, folks!

[brosnan]

Well, the TLC555 based "fake speed signal" version of the
nav speed lockout seems to work. When the switch is
flipped away from "normal" to "defeat", it gives continuous
access to the map features which are normally blocked
when moving. No need to flip the switch back and forth
to avoid GPS speed lockout. Since it fakes movement at
about 4mph, the map position is not accurate until a few
seconds after the switch is flipped back to "normal".

Some soldering is required, as you can see from the photo
below. You'll also have to cut the violet wire to the
Nav ECU. It can be found behind an A/C outlet as shown
earlier in this thread.

I used a magnetic switch from Hometech for ESD isolation
(http://www.hometech.com/security/acc.html#AS-507381BW)
but a normal toggle switch (SinglePoleDoubleThrow) will also
work. You should find all the parts at Radio Shack. If you
can't find exact values for the 27KOhm resistor you can
substitute anything from 10K to 100K. If you can't find
the exact 0.22uF capacitor or 820KOhm resistor, you can
choose similar values but keep the product of the two about
0.18seconds. That will keep the output frequency around
the same 4.7pulses per second that I've got. Too fast and
you'll get the speed sensor lockout. Too slow and you'll
get GPS speed lockout (and some other odd effects).

The oscillator board consumes about 2mA from the 13.5V
supply, so you should connect it to switched power. For
example, the "cigarette lighter" outlet is an easy spot to tap.

Eventually I see this being driven by the DEST and MAP, etc
buttons as discussed earlier. But this part's ready now in
case anyone wants it. As they say, some assembly required.
Install at your own risk.
Drive carefully!

[brosnan]

Here's a way to implement an automatic version of the
phone speed lockout defeat. When you press the "off hook"
phone button on the steering wheel, the speed signals
to the MultiDisplay are blocked to allow full access to
phone touchscreen items. When you press the "on hook"
button to hang up, the speed signals are restored.

I had in mind a simpler single chip version based on
a microcontroller. However, since many of you will not
have access to the tools for that, I've opted for a circuit
using readily available components needing only some
soldering and wiring onto a printed circuit board. If you're
not comfortable building and testing circuits like this,
you should probably stick with the manual switch method
described earlier in this thread. But if you'd like the
"switch free" automatic method, read on.

The schematic, board photo and location of the wire from
the phone switches is shown below. The phone switches
share the same wire as the MODE button. It's called AU2
in the repair manual and is most easily accessed at
center connector #2 pin 5B-2. That's behind the A/C outlet
just to the right of the radio. It snaps off if pulled toward
the back of the vehicle. This wire goes to about 1.68V when
the off hook button is pressed, about 0.75 volts for on-hook
button, about 0V for MODE button and about 4.3V when no
button is pressed.

The circuit uses a window comparator to detect when the
off hook button is pressed. That clears a flip flop which
causes blocking of the speed signals to the MultiDisplay.
A single comparator detects lower voltages from the
on hook (or MODE) buttons and sets the flip flop, restoring
the speed signals. The set signal is slow to rise so at
powerup and while swinging rapidly through the window
comparator range, we allow speed signals to pass through
as in normal operation. The variable resistors need to be
adjusted to the 2 indicated DC values on the schematic.

While making a call, you will have access to numeric
dialing, phone # display and the full phone book. You
will lose some info for the 5 minute MPG bargraphs while
in this mode, so don't be surprised if you see some
funny or missing bars after a long call. When done with
the call, press hangup and all will return to normal.
If you pop over to the Consumption screen without pressing
hangup (or MODE), the animated tires will not be spinning
and you won't get an auto reset of the trip distance after driving away from a fillup.

[brosnan]

For those electronics-minded Prius fans out there, here's a circuit which
lets you access all nav and phone features while moving without flipping
any switches. It just fakes slow (or no) speed signals to the Nav ECU
or MultiDisplay as appropriate. When you press DEST, INFO or MENU
it sends ~3mph fake signals to the Nav ECU while you use features
on those screens. Then when you pop to a different screen
(press either MAP button, CLIMATE or AUDIO), it restores the
speed signals. When you press the Phone OFF HOOK button
to make a call it breaks the speed signal connection to the
MultiDisplay until you press the HangUP button.

This project involves removal and modification to the expensive
MultiDisplay unit, so it's definitely a do at your own risk project!

Let me know if you want more pictures or details.
Drive safely!
[edited in better schematic]
schematic now here: http://www.wb5mrn.com/prius/schemati...to_defeat5.pdf

[efusco]

Brosnan,
That is an absolutely fantastic solution. I would love more details about the install. That mess of wires on the floorboard is a bit intimidating the way it's laid out and it isn't clear to me what wires you're splicing into and where they come from.

You're definately breaking new ground in a very sweet way.

Does that fake signal throw off the mileage calculations on the Consumption Screen?

[brosnan]

OK, I'll write up more detailed instructions with some photos.
For now, just a few extra comments.

The wires needed come from 3 locations:
6 wires from the MultiDisplay.
5 wires from the Center Connector #2 behind the A/C outlet just right of the radio.
2 wires for power and ground from the "cigarette lighter" socket.

As far as I can tell, this modification does not affect the average
MPG or trip distance shown on the Consumption Screen.
The bar graph history is affected by phone usage. If you're
on the phone for more than 5 minutes, you'll have some
blank bar graph elements.

By the way, I'm giving up on the "I agree" auto-press function.
It sure would be nice to have a "magic finger" press the "I agree"
soft button for you every time the map is brought up after each
powerup. I had a look inside the MultiDisplay and you'd need to
dissassemble more of it than I care to in order to solve this
annoyance. So that challenge is left to the group!

[brosnan]

Attached below is the material list for the dual auto speed lockout defeat schematic above in post: http://www.priuschat.com/forums/viewtopic....p?p=24399#24399

Also 2 more photos showing which cable bundle in the MultiDisplay to tap into.

material list:http://www.wb5mrn.com/prius/material...uto_defeat.pdf
the 2 photos:http://www.wb5mrn.com/prius/which_cable_to_tap.jpg and http://www.wb5mrn.com/prius/heat_shrink_and_solder.jpg

[brosnan]

If you're interested in a switch-only manual version of the speed sensor defeat, here's the simplest one I know of:

1) Find a Single Pole Single Throw switch such as Radio Shack 275-612 ( http://www.radioshack.com/product.asp?cata...ct%5Fid=275-612 ) You can also use an SPDT,DPST or DPDT switch but will only use two terminals.
2) Gain access to center connector #2 as in above post ( http://priuschat.com/forums/viewtopic.php?...p?p=22788#22788 )
3) Cut the two violet wires from 5E-11 and 5E-12.
4) Tape up the wire still attached to 5E-11 with good electrical tape. It's not needed.
5) Extend the length of the wire still attached to 5E-12 so that it can reach the switch location. Tape up the connection to prevent shorts.
6) Join the remaining two violet wires together and also to a new wire extending to the switch location. Tape up the connection.
7) Solder the extension wires to the two switch terminals (if SPST) or to a middle terminal and either adjacent edge terminal if not SPST.
8 ) Mount the switch in an accessible spot (in the A/C outlet panel? or the panel under the radio?)

When the switch is closed, the speed sensor signal will be passed on the nav and phone functions, so you will see the normal lockouts when moving.

When the switch is open, the speed sensor signal will be blocked and you will not be locked out. After about 1/2 mile of driving, the nav secondary lockout will occur and you'll need to flip the switch back and forth to get more time.

The known side effects while the switch is open are:
1) 5 minute MPG bargraph display in consumption screen will be altered
2) Animated tires don't spin on the consumption screen
3) Auto zero of the trip distance on the consumption screen won't occur after a fillup.
4) After choosing a destination while moving, then closing the switch, it may take ~30 seconds for the map position and voice instructions to become accurate.
5) Your dealer may hassle you about the odd wires if it's in for repair.

If you live in a place where static electricity is a big deal (say Colorado for example), you should probably ground the metal shell of the switch or use a long insulated switch paddle. It would be a shame to zap the input of the expensive nav ECU or MultiDisplay.
Do at your own risk.