Navigation - Parking Brake Simulator

[sweeneyp]

Well I'm looking to make something to make my navigation system think the parking brake is on (already building speed sensor override for the lock-out). The parking brake emulator is meant to allow the OEM rear dvd player to play video on the front screen while the vehicle is moving.
Now from looking at the Toyota docs, it looks like all the parking brake is, is a switch that grounds the headunit. So when the brake is enabled, the headunit is grounded on that wire, and not grounded when the brake isn't enabled. These are the docs I was looking at (below) does that sound right? I was just making sure before I actually try it and acidently mess something up in the rather expensive headunit . If its as simple as that, I'll cut the line and run it to a ground (with an inline rocker switch so I can only manually enable it, not a constant ground). I think (if you look at the first picture) the grey box with the 1H and 1C sockets is a control box/splitter for the parking brake switch that also feeds into the parking brake light and other parking brake activated systems. By cutting the original wire I would only be creating the ground for the headunit and not the rest of the car's systems. Let me know what yall think.
Thanks

(and to make sure its clear, the top blue box in the top pic is the headunit, I just cropped the diagram to only show the parking break wire portion)

[RunDeep]

It looks like it is just a switch to ground that does it, however, it looks like the sense is reversed, i.e. when the brake pedal is pressed the switch is open and when it is released the switch is closed. Normally you would draw the switch in its inactive state which I would think matches when the bake pedal isn't pressed. Also, the last figure says the resistance is low when the shaft isn't pressed and high when it is, not sure what it looks like mechanically?

If you don't have a multimeter (you can get an ok one cheap), you could just get a 12 V lamp, connect one end to 12 V and the other to the wire running to the switch (or the switch directly if you can pull off the connector). If it lights up right away then the switch is normally closed and vice versa. If the switch opens when the brake pedal is pressed then you wire it this way (and only the head unit is affected); ON means the nav system thinks the brake is engaged:



If I'm wrong and the switch closes when the brake is pressed then you have to wire it up differently. Doesn't matter where you make the connection between the switch and the head unit:



Please note however, if the 1H/1C block is a terminal block that ties the switch electrically to other inputs then when you ground the lead to the head unit, you will ground everything attached to the terminal block too. Doesn't matter if you attach to the wire between the switch and 1H/1C or between the head unit and 1H/1C. You could get around it by putting in diode (probably) but is it worth it? Would there be any problem with turning on the other stuff?

Good luck, just picked up my 2012 hybrid, may want to do the same thing so let me know how it turns out.

[sweeneyp]

Thanks for the reply,
well I had planned to cut the ground wire between the radio and terminal block to prevent grounding the other components. Like the first pic, but instead of having the ouput of the rocker reconnect to the wire, I would have it go to the chassis. If you ground all the components you are going to get the dash warning light to come on, and if the car is moving while the parking brake is enabled, the car will beep at you, this should prevent that.

I believe the way the brake works mechanically, is when it is off it compresses the switch closing the circuit. And opens when the pedal is pressed. That is why you get the parking brake light to come on before its actually engaged (when you barely press it) and you don't have to press the pedal in a certain distance to activate the circuit.

I'm waiting on parts for my navigation lockout override to get here (waiting on company to ship) so it looks like they won't be here till late next week. I had planned to check this when I had my headunit/dash apart installing that. So I'll update this in awhile when I finally get to the point of installing that component where I can test it. Just kinda curious what people though, and was in the planning phase right now.

[RunDeep]

If the switch is normally closed and opens when the pedal is pressed then you don't need to add any ground connections. With the switch closed (brake released) the entire path is grounded and you just need to break the link with the head unit, everything between the OEM switch and where you make the cut will stay grounded. Just hook it up like the first picture where you add a switch in the connection between the head unit and the terminal block.

If it turns out to be the other way then a better approach than picture two is to use a double throw switch like this. It will isolate the head unit and leave everything else alone when you throw the switch.

[sweeneyp]

well I completely blanked about the possibility of using a SPDT rocker there, nice idea. If this works I'll definitely do it like you have it done there.
thanks!
Found what I was looking for in my docs (position of switch in assembly)

It is in the off position when the pedal is not engaged. That little arm looks like it keeps the switch compressed and as soon as you move the parking brake to engage it, even a little, it uncompresses the switch cylinder. That appears to trigger the ground on the circuit. So it looks like scenario 2 of what you said in your last post

[jcayer]

How are you building the nav override? any diagrams/schematics for that?

I don't have the rear entertainment system, but would be interested in seeing your plan for allowing the nav to work while driving... kinda hate that my wife can't enter a destination while I am driving...

If you are successful in creating a bypass circuit/switch to allow the nav controls while moving, this would make for a AWESOME sticky thread in the forum...

Good luck!

<Subscribing>

[sweeneyp]

Originally Posted by jcayer

How are you building the nav override? any diagrams/schematics for that?

I don't have the rear entertainment system, but would be interested in seeing your plan for allowing the nav to work while driving... kinda hate that my wife can't enter a destination while I am driving...

If you are successful in creating a bypass circuit/switch to allow the nav controls while moving, this would make for a AWESOME sticky thread in the forum...

Good luck!

<Subscribing>

sticky for the override already exists (Nav override install in 2011 Highlander) I finished building the circuit a few days ago, will install it soon. When I install that, i will test the parking brake override theory to see if it works. If so 1 switch will allow for dvd playback and nav override (using 2 relay's)

[J.A.]

Video on Nav is pretty cool. Hope your install is as easy as grounding the E-Brake. Here is what I had to do to get video on my 4R nav w/o rse.

Video on Nav Mod

[sweeneyp]

Well after a very long time, I finally got around to testing this. (I was actually installing a nav override that J.A. designed (thanks again for the schematics J.A. ), and a 400 watt power inverter mounted under the shifter). I used a standard SPDT relay to control it (I used a relay because the was built in with the nav override so that 1 switch activated both the p-brake emulator and the override)

Needless to say, if you separate the ground you are making from the rest of the circuit and only give it to the headunit, it works perfectly. The headunit will detect the parking brake at any speed, and the rest of the car does not think the parking brake is on.

And now for the bad news ..... I did this so that I could have video from my OEM dvd player on the nav screen..well it didn't work for that. With the override the headunit needs a speed of <4mph to keep the system from locking up. With DVD playbay I assumed it would only need the parking brake, but no. It needs the parking brake and zero mph reading on the speed sensor. I had wired the emulator into my override so the headunit was always getting 3mph and the parking brake and it didn't allow the video to come up. So I'm going to have to go back eventually and add another relay that will interupt the speed line while the parking brake emulator is on (to make it read zero), and keep the circuit intact while the override/normal operation is occuring.

[ldeveraux]

Keep updated on your progress. It beats paying 200-300 for one of those lockpick units. Keep up the good work!

[sweeneyp]

Thanks, Ideveraux

Ok update time, I installed another double throw relay between the nav override and headunit on the speed line (so that when the relay is not energized the signal passes through, but as soon as it is energized, it breaks the circuit). That does work to make the headunit think the car is not moving. And it worked great, with both my parking brake relay grounding the unit and the speed relay disabling any speed input to the headunit, I had the OEM dvd player showing on the screen driving down the road for about two minuets......

BUT, it seems that if the headunit detects no speed input while the GPS antenna is picking up movement, after a period of time (~2 min in my case), it ignores the speed line's input and updates the location from the antenna. Unfortunately this also makes the headunit use the GPS antenna for the speed and knocks off the video (simply disabling and reenableing the override + other relay's fixes this, but I don't want to have to do that every 2 min). So I'm going to see if there is a way to interrupt the GPS signal (like I did with the speed line signal). My electric wire diagram for the JBL system/headunit is not showing the GPS antenna so I gotta do some more research on this

If I get all of this to work, I'll make a diagram to show everything I did (I'm sure everything I'm typing is just getting confusing at this point...).

Edit: I believe I know which plug (single pin socket) the GPS antenna on the back of the headunit, quick question though. Does anybody know if the cable would be some kind of special cable (coaxial, fiber optic etc...) I am hesitant to cut into a wire like this to install a relay/switch.

found this in my toyota docs though (concerning navigation ECU):
Distance correction: The running distance signal from the vehicle speed sensor includes the error caused by tire wear and slippage between the tires and road surface. Distance correction is performed to account for
this. The navigation receiver assembly automatically offsets the running distance signal to make
up for the difference between it and the distance data of the map. The offset is automatically
updated.
Simple "feature" giving me all these troubles haha

[sweeneyp]

Ok, well I've been looking this up and it would seem that its a coaxial cable (between the antenna and headunit). I think I'm just going to leave it be and stop this project, coaxial are just too easy to mess up (and not as easy as cutting the wire, wiring an inline relay, and being done). I just don't want to damage teh OEM antenna wire and have to get a new one.

So summing everything up in this thread so not to confuse anyone who reads it:

1) if you take the headunit parking brake wire, wire it up to either a double throw switch or relay (the shared terminal going to the headunit, one terminal going to a ground, and the other terminal going to the OEM parking brake circuit) if will make the headunit think the parking brake is on, and the rest of the car (lights on dash, beeper alerting to parking brake is on) will not activate.

2) above when combined with the nav override (speed sensor override), and a relay (another double throw relay (pin 87a going to headunit, pin 30 going to override, when energized it will break the circuit)) between the override and headunit on the speed input wire will allow the OEM dvd player to come up on the screen. But, it only last a min or two before the navigation ECU ignores the speed input and uses only the gps antenna, which internally sets the vehicle speed, locking out the dvd playback. I'm guessing that somehow removing the antenna signal during those times allow it to work, but its too expensive a part/finicky equipment to chance installing an inline relay to break the circuit.

I'm not sure how those coastaltech lockpicks get it to work...but I'm clueless and am throwing in the towel