Navigation Input Override (Speed Sensor Bypass)

Well, as I warned, haste makes waste. I've discovered a couple of errors, and determined that I need to use two separate 555 timers instead of one 556, since they need to be independently power-switched. New schematic is attached - but still unverified. Note that the switch is moved off the schematic, and I just have a J1 connector labeled with what wires should be connected. "SW WIP" is the wiper of the switch, "SW (ON)" is the momentary contact, "SW ON" is the "switched" contact.

I probably won't verify this until late this weekend - Ill be spending most of my weekend removing the entire dash to wire an auto headlight mod.

 

Hope not - especially with your great instructions and photos. thanks again for those!

 

I'm not that picky either.... heck.. even having to reset it every 30 seconds I could live with if needed.

 

well, i cut the purple one in the middle. there is another wire that could be construed as purplish maybe. and i did get the loss of GPS at first where it updates like every 10 seconds for a bit before it kicked back in.

i will disassemble sometime soon and reconnect wire and double check settings.

 

There is a company called Prestigious Society that offers 100% plug and play navigation and video override for Lexus and Toyota.

From it's News section, they are looking for 2010 Prius to test fit their override solution.

 

Good find! Since you're under 5 posts, I'll post the link:
Override GPS navigation | Lexus | Toyota

I'm curious to see if it works. And if it differs from the above hardware solutions.

 

"Prestigious Society" is intriguing, and if they can override without the positioning issues, I'll be interested...

But I wonder if they will provide effectively the same solution already presented here. Be interesting to keep an eye on them and see what develops.

Thanks for the find!

 

i checked their catalog and Prius is not listed

 

Looks like they are in California... maybe someone can call them and find out whats the scoop on prius?

 

The scoop on Prius was detailed by soaristo in the original post on this company:

So if you live in CA and want to volunteer as their guinea pig, get in touch with them.

 

Hi Guys
New to this thread.....so

I'm after some information reagrding the shape/format/voltage level of the signal that is NORMALLY carried on the violet wire from the MFD to the NAV ECU (Prius 2008).

What I need to know is:

1. When the vehicle is NOT rolling, does the signal return to zero volts (ground)
2. If the signal is digital, is the speed information contained in the frequency of the signal. If so what is the frequency of the signal when the wheels are not rolling?
3. If the signal is digital is it 5vp-p? (some posts here suggest it's 12v...if this is true then it's not digital.)
3. If the signal is digital and PWM is the speed information contained in the mark/space ratio of the digital stream?

Reading between the lines, it's obvious that I want to know what the signal is doing when the wheels have stopped rolling. I'm not interested in the signal status when the vehicle is moving.

If anybody can assist, it would be greatly appreciated.

Regards from OZ

Ray

 

I haven't put an oscilliscope on it, so I cannot give you actual measurements. But the repair manual states that it is a pulsed signal, 4 pulses per tire revolution (http://priuschat.com/forums/gen-iii...-override-speed-sensor-bypass.html#post926996). So I think what you're looking at is more like encoder output than a PWM digital stream. There are no pulses when the wheels are not rolling. Based on successful bypass efforts posted brosnan (http://priuschat.com/forums/gen-iii...-override-speed-sensor-bypass.html#post931393) and others, it appears the pulses alternate between 0 and 12V.

 

The 2008 model has 4 wheel speed sensors which put out an ac signal varying in frequency and voltage level. These four signals are fed into the Skid ECU, and apparently some averaging is done (don't know the algorithm used), before the signal is then passed onto the MFD and the Nav ECU.

This signal may undergo some conditioning before it is sent to these devices, and this is where my dilemna begins.

However, if the pulses disappear when the vehicle is not rolling, then this situation suits my purposes exactly as I would want.

Can anybody confirm?

and thanks to rachaelseven

Ray

 

Again, no physical measurement, but the diagnostic screen of the NAV system does show a pulse count. And I watched the count go to zero at a standstill and come up as the car began to move. Only software feedback, so not as conclusive as a direct measurement of course, but in concert with the statement by the repair manual that it is "4 pulses per revolution", it seems pretty solid.

 

I have looked at the signal on an oscilloscope. Note that this signal that we are cutting is NOT coming directly from any wheel sensor - it is coming from the combination meter assembly.

1. Actually, I believe it returns to 12V at a stop. See explanation below.
2. The combination meter is controlling the frequency of the signal, which stays at approx 40% duty cycle when the vehicle is in motion - at least that's what I have observed. This matches the TIS diagram posted elsewhere in this thread. I didn't try to go 0.5 mph to see what the duty cycle was.
3. And yes, it is digital, and at approx. 12V - (Digital signals can be at any logic level - 3.3V, 5V, 12V..) But the signal is pulled high at each respective ECU (or the NAV unit, in this case) that uses the signal (depending upon vehicle options), to whatever logic level that ECU requires. The combination meter, which gets its input from the wheel sensors, simply grounds the inputs into the ECUs, providing the low side of the pulse to all utilized ECUs. Here is the explanation from TIS:
==========

DESCRIPTION
The combination meter assembly (No. 3 meter circuit plate) receives the vehicle speed signal from this circuit. The wheel speed sensors produce an output that varies according to the vehicle speed. The wheel speed sensor output is received by the skid control ECU which uses this information to create the vehicle speed sensor signal*1. The vehicle speed sensor signal consists of pulses sent to the combination meter assembly from the skid control ECU. To create this signal, 12 V is output from IG2 which is behind a resistor in the combination meter assembly. This voltage is sent to the skid control ECU. The pulse signal is created by switching the transistor in the skid control ECU on and off, making the voltage on the wire drop to 0 V. A similar system is used for the output of this signal from the combination meter assembly via terminal +S. A voltage of 12 V or 5 V is applied to terminal +S from each ECU or relay that is connected to this terminal. The transistor in the combination meter assembly is controlled by the signal from the skid control ECU. When this transistor is turned on, this transistor makes the voltage supplied by the various ECUs (via their respective internal resistors) drop to 0 V. Each ECU connected to terminal +S of the combination meter assembly controls its respective system based on the pulse signal.​

===========​

Hope this helps.

 

Jayvee

Looks like you have nailed it.

Actually, there still is signal present (as you have observed) when the vehicle is motionless. The 4P output is present when the vehicle is not moving, and engine is at idle speed, and looking at the cro waveform in the meter/gauge manual, it is about 12vp-p

I can work with that.

thanks again jayvee

Ray

 

They're in Southern California (La Habra) if anyone's interested.

 

I just send them an email to see if they need a test car or anything. It sounds like they unlock full video input to the nav screen as well as allowing the use of the existing features while in motion. Their units are not cheap at over $200 but who knows...it may be worth it to some...

 

Would be worth it to me for sure!