The reason for this mod is that Toyota disables some key navigation functions while the vehicles is in motion. For example, you can’t enter a destination address, or refine POI filters. These are functions that the driver should certainly not be doing while in motion but I don’t see why the front seat passenger can’t be allowed use them.  After all, the passenger seat does have a sensor to detect if someone is sitting there.

Proceed at your own risk with this mod.  The driver should pay 100% attention to the road and not be distracted by use of the nav.

Inspiration for this mod comes from PriusCar.com.

The key to this mod is Toyota part #82998-12690, a terminal repair wire. This allows modification of the circuit without cutting any wires. In theory, this mod is simple, interrupt the VSS (Vehicle Speed Sensor) signal going to the nav ECU and the nav thinks its stopped. After some motion, the ECU GPS information will conflict with the VSS derived position and the nav will correct and remove the functions again. An electronic timer can be used to periodically open/close the VSS circuit and fool the ECU.

These are the connectors going into the navigation ECU under the passenger seat.  The connector I modified is the large one on the right (the one where you see the pink wire) First step is unplugging all the connectors from the nav ECU. The VSS wire is the violet/white wire at position 5. This wire needs to be intercepted. That is, the signal going into the ECU from this VSS wire needs to be rerouted to a switch or timer and then sent back into the ECU. One way to do this is to cut the wire and solder an extension in place.  I did not want to do this so I purchased part #82998-12690. This part is a new female contact & wire that can be put in place of the VSS wire in the connector.  Step #1 is removing the VSS contact from the connector and replacing it with the part #82998-12690. This handy page at PriusCar.com explains how to remove the wire from the connector.  The Sienna connector is not exactly the same but close enough.  The white part of the connector you can see on the 2 left images needs to be popped up.  It does not come off, only pops up about 2 mm to release release 1 retainer on the contacts.  Next, as described in the above web page, you need to insert a small, narrow tool into the slot below the contact to open the locking lug. Then pull the wire out from behind. Easier said than done, this part took the longest of the whole project.  I used a very small jewelry style screwdriver. Be careful with your tools, the blue/yellow wire is 12+ constant.  When removing the wires, pay attention to the orientation (there is a little metal flag on the contact that faces down) Two other wires that need to come out are the gray at position 18 (ACC 12V+) and white/black at position 17 (ground).  These 2 are used to power the timer.  There are other places to get 12+ACC but using the nav connector keeps the wiring very simple.  I selected a length of CAT3 phone cord for the extension (4 wires - 2 for power & 2 for the VSS signal in/out). Wire colors I selected on the CAT3 are Solid Orange=12+ACC, Solid Blue=Gnd, Orange/White=VSS in (to switch), Blue/White=VSS out (to ECU).  12V+ACC & ground only need to be tapped.  I inserted about 1/8” wire between the clamp and insulation of the connector then soldered the solid CAT3 wire to the stranded wires. Use only a small drop of solder, you don’t want to bulk up these contacts. For the purple VSS wire, I stripped off about 1/2” of the orange/white and bent the wire in half. Then I inserted the folded wire into the female end of the connector.  It makes a good connection without the need to solder. The last wire is the VSS return, this one just solder to the 82998-12690 part. When everything is soldered, I used electrical tape to insulate the two exposed VSS junctions. Next I plugged the 12V+ACC and ground wires back into the connector, they click when they are locked in place. When plugging the connectors back in, make sure the little metal flag on the contact faces down. The image shows the completed connector all zip tied and neat. You can hardly tell any modifications have been done.  This mod is 100% reversible. On the other end of the CAT3 wire I installed an Altronix timer in a small project box.  Since I was using telephone wire, I decided it would be appropriate to use an RJ11 jack to plug the wire into the project box.  I highly recommend some sort of connector so the timer can be removed if necessary.  To the right is an image of the timer and wiring.  J1 & J2 on the timer should be cut. DIP positions 1, 2 & 3 should be ON, position 4 off. I highly recommend testing the circuit with a 9V battery to verify operation and calibrate the potentiometer to approximately 20 seconds.  The LED will indicate when the relay is energized.   Left is the schematic of the circuit and above the completed circuit in the project box. Operation is simple - with the switch in position 1, the VSS circuit is completed by the switch and no power is supplied to the timer. Switch in position 2 and VSS is interrupted by the switch and the timer is given power. The timer will momentarily close the VSS circuit approximately every 20 seconds.     To test, start the car and put the nav in diagnostics mode.  The NAV Vehicle Signal Check screen should look something like this (0 speed) when VSS is open even with the car is moving.  Pulse will only increment when VSS is present.  Speed will be 0 when VSS is open but pulse will remain at the last count. Opening the VSS switch will give full control of navigation functions for 20-30 seconds until the ECU determines that the GPS conflicts with the last position.  The timer will automatically open/close the VSS and keep the functions active. Note: There are two “Signal Check” screens, one for the nav display and one for the nav ECU. Be sure you are looking at the right one. To the right is the completed project with the switch/timer box mounted on top of the NAV ECU with double stick velcro.  The toggle switch is circled in red.  The passenger just needs to reach under the seat and activate the switch.  A click will be heard every 20 seconds or so until the switch is moved back to the normal position. Note that the NAV will get a bit lost temporarily while VSS is interrupted as the NAV ECU relies heavily on the speed sensor to determine position. If entering an address, deactivate the switch as soon as the route is calculated.  It may take 30 seconds or so for the ECU to re-determine the position based on the GPS.