Installing aftermarket in-dash GPS unit in a 2015 Prius Two

This post documents how I installed an aftermarket in-dash GPS unit (a Pioneer AVIC-8100NEX) in my 2015 Prius Two. I will mainly focus on the wiring connections that need to be made behind the dash since that's the thing that took me the longest to figure out. This post will not cover removing the dash, the original head unit, or the other parts of the new head unit (like GPS antenna and microphone). It is easy to find instructions on how to remove the dash (start with YouTube).

All the information provided here is correct and accurate to the best of my knowledge. Some information is solely based on observation or measurements I've made on my 2015 Prius Two (standard hatchback) and may not apply to your vehicle. Of course, this information comes with no warranty whatsoever.

Required parts

• 2015 Toyota Prius Two (standard hatchback) with standard rear view camera,
  Display Audio system (not Navigation), and without the JBL speakers
• Pioneer AVIC-8100NEX (Amazon.com)
• Scosche TA02B wiring harness (Amazon.com)
• Metra AX-TOYUSB USB port cable (Crutchfield.com)
• Lots of wire connectors, e.g. Posi-Twists (Amazon.com)
• Jumper wire with 1-pin female connectors (e.g. Amazon.com)
• 12 V to 6 V DC converter (e.g. Amazon.com)
• 3.5 mm to 3 RCA cable (e.g. Amazon.com)
• 16-pin female connector TE Connectivity 1318382-2 (e.g. Mouser.com)
• 28-pin femail connector TE Connectivity 1565373-4 (e.g. Mouser.com)
• Electrical tape (e.g. Scotch 33+)
• Steering wheel controls interface (Amazon.com)
• Metra 40-LX11 antenna adapter cable (Amazon.com)
• Additional USB port (e.g. eBay.com)

Connectors
The pins are numbered left to right and top to bottom when viewing the connector as shown in the pictures. [NC] stands for "not connected" and means that the pin on the connector has no wire connected to it. The colors refer to the color of the cable in the car connected to that particular pin.

White 6-pin and 10-pin connectors


Left: 6-pin connector, right: 10-pin connector

6-pin connector (top: pins 1 - 2, bottom: pins 3 - 6)

1. (red) right rear speaker (+)
2. (black) left rear speaker (+)
3. (white) right rear speaker (-)
4. [NC]
5. (black/white) Dimmer for radio illumination (with the parking or headlights on, this pin carries 0 V (with respect to the ground, which is pin 7 on the 10-pin connector) if the dimmer is turned all the way up and the voltage increases as the dimmer is decreased, the maximum voltage is about 10 V, which corresponds to the lowest dimmer setting)
6. (yellow) left rear speaker (-)

10-pin connector (top: pins 1 - 4, bottom: pins 5 - 10)

1. (light green) right front speaker (+)
2. (pink) left front speaker (+)
3. (gray) ignition power (12 V when POWER mode is ACC or ON, or when hybrid system is running)
4. (light blue) constant power (12 V regardless of whether POWER is turned on or not)
5. (blue) right front speaker (-)
6. (purple) left front speaker (-)
7. (brown) ground
8. [NC]
9. [NC]
10. (green) radio illumination (12 V when parking lights or headlights are on, unaffected by dimmer setting)

Gray square connector



This is the connector for the USB port that is located inside the center console. Use the Metra AX-TOYUSB adapter to connect this USB port to the new head unit. WARNING: Make sure you get AX-TOYUSB and not AX-TOYUSB-2.

White 16-pin connector



16-pin connector (top: pins 1 - 8, bottom: pins 9 - 16)

1. [NC]
2. [NC]
3. [NC]
4. [NC]
5. [NC]
6. (red) parking brake input (about 13 V when parking brake is DISengaged, 0 V when parking brake in ENgaged)
7. (white) 6 V power supply for the rear view camera (The radio provides 6 V on this pin when POWER is ACC or ON, and the hybrid system is running. Interestingly, the camera is being powered in any gear (I tested P, D, and R). The only situation I found where the radio shuts off power to the camera on this pin is when the gear switches from P to D. But if I switch from P to R and then to D, the power remains on this pin and it carries 6 V.)
8. (red) rear view camera signal (+)
9. [NC]
10. [NC]
11. [NC]
12. [NC]
13. [NC]
14. [NC]
15. (orange) ground for the 6 V power supply on pin 7
16. (black) rear view camera signal (-)

White 28-pin connector



28-pin connector (top: pins 1 - 14, bottom: pins 15 - 28)

1. (black) ignition power (12 V when POWER mode is ON, 0 V when OFF or ACC)
2. (pink) reverse gear signal (about 14 V when in reverse, 0 V otherwise)
3. [NC]
4. (red) probably 6 V power supply for microphone (not tested)
5. (black) probably microphone signal (+) (not tested)
6. (green) probably microphone detection (not sure how that works and did not test)
7. [NC]
8. [NC]
9. (green) probably CAN communication (not tested)
10. (white) probably CAN communication (not tested)
11. (orange) probably ground for AUX detection (not tested)
12. [NC]
13. [NC]
14. [NC]
15. [NC]
16. [NC]
17. (purple) speed pulse wire (aka vehicle speed sensing or VSS wire)
18. (yellow) probably ground for microphone detection (not tested)
19. (white) probably microphone signal (-) (not tested)
20. [NC]
21. (red) steering wheel controls (SWC1)
22. (green) steering wheel controls (SWC2)
23. (pink) ground for steering wheel controls (This pin needs to be connected to ground for the right-hand steering wheel controls (AC controls, DISP and TRIP buttons) to work, I tested this by completely unplugging the radio and trying out the steering wheel controls. The controls did not work when this pin was not grounded, but connecting this pin to pin 7 on the 10-pin connector (which is ground) made the right steering wheel controls work again, with the radio completely removed.)
24. [NC]
25. (pink) probably AUX detection (not tested)
26. (black) right AUX signal (+) (the AUX jack is located inside the center console right next to the USB port)
27. (white) AUX signal signal (-) for both left and right
28. (red) left AUX signal (+)

Antenna connector



There are two coax connectors and one wire connector. The wire on the side between the two coax connectors carries 12 V, which should be power for the antenna. I'm not sure whether the two coax connectors go to different antennas.


Connecting things

6-pin and 10-pin connectors

To connect the wires on the 6-pin and 10-pin connectors to the new head unit, I used the Scosche TA02B wiring harness. The colors of the wire on the harness match the colors of the wires on the power connector of the Pioneer AVIC-8100NEX (but double check with the notes above and the Pioneer installation manual). I decided to go the reversible route and not solder anything. So I'm splicing the wires and use Posi-Twist wire connectors.

Start by connecting the speaker wires (those are straight forward): white and white/black for the left front speaker, gray and gray/black for the right front speaker, green and green/black for the left rear speaker, and violet and violet/black for the right rear speaker.

Also connect the yellow wires (constant 12 V power) and the orange wire of the Scosche harness with the orange/white wire of the Pioneer connector (this is for the radio illumination, aka lighting switch).

I'm installing an additional USB port (actually two additional ones, one that will connect to the Pioneer unit and one that will only carry power). The additional USB port needs to be connected to power. I thought about connected it to the power cable that's always on so that one could use it to charge even when POWER is OFF. But then I decided to connect the USB port to the switched power, so that there is no possibility of draining the car's battery if something is left plugged in the USB charging port. The USB port also needs to be grounded.

There are a number of things that need to be connected to ground and pin 7 on the 10-pin connector is the only ground we've got (I'm pretty sure the other pins that are ground get grounded internally by the factory radio, so we have to make sure we ground them, if we need them.

The following things need to be grounded, i.e. connected to the black wire of the Scosche TA02B harness:

1. Pioneer unit (on the Pioneer power connector)
2. Rear view camera power
   
3. Steering wheel controls module
4. Additional USB port
   
5. Pin 23 on the 28-pin connector

The following things need to be connected to 12 V switched power, i.e. connected to the red wire of the Scosche TA02B harness:

1. Pioneer unit (on the Pioneer power connector)
2. Rear view camera power
3. Steering wheel controls module
4. Additional USB port
5. Antenna

Since I got the small Posi-Twist wire connectors, I can't splice all 6 wires together at once, so I used some ordinary speaker wire to daisy chain the ground and switched power connections.

Here is the wiring harness at this point.



Note the two unconnected speaker wires on the right attached to the red and black wires for daisy chaining the switched power and ground connections. The long light green wire on the left is the parking brake wire of the Pioneer connector, which we will connect later. On the ground connection I've added jumper wire with a female connector that will plug into pin 23 of the 28-pin connector. Also note that I haven't yet connected the ground wire of the Pioneer connector (long black cable on the right). This will be connected to the ground with a later daisy chain link.


16-pin connector for rear view camera

The 16-pin connector contains the connections for the rear view camera and the parking brake signal. The camera requires 6 V power and so I got a 12 V to 6 V DC converter, because the only power source we have available is 12 V. I got this one. I considered making my own converter by following this guide, but the integrated circuit used there is a linear voltage converter, which is quite inefficient and thus would produce quite a bit of heat. So I decided to buy a converter on Amazon (link above) that claims to be >96% efficient and will thus produce much less heat. That being said, I guess that the heat produced by a linear converter is probably not a problem because the camera doesn't draw a lot of current.

To make the installation as simple as possible, I got a female connector that fits the 16-pin connector (TE Connectivity 1318382-2) to make my own harness. The jumper cables simply plug into the pins of the connector (which are actually intended for soldering). We use pins 6 - 8 and 15 - 16. Here is the connector with the cables plugged in:



To protect the thin pins and to avoid the jumper cables slipping off the pins, I wrapped the connector with electrical tape. I also put electrical tape between the two rows of pins:



Now we take our 3.5 mm to 3 RCA cable (picture below) and clip off the yellow RCA jack. This will become the video RCA jack for the rear view camera.



Connect the ground wire of the RCA jack (the wire connected to the outside ring of the jack) to pin 16 and the central wire (connected to the central prong of the jack) to pin 8 of the 16-pin connector. That's the camera signal. Now connect the output wires of a 12 V to 6 V DC converter to pins 7 (+) and 15 (-, ground). This will provide 6 V of power to the camera. Finally, pin 6 will be connected to the parking brake wire of the Pioneer connector (green wire in picture below). This is what it looks like with the wires taped to the voltage converter. The red and black wires connected to the voltage converter are its input wires. The black wire will be connected to ground and the red to switched 12 V power. Alternatively, you could connect the red wire to the reverse gear signal, so that the camera only gets power when the car is in reverse, but since the factory radio seems to provide power to the camera even when the car is in D, I decided to power the camera whenever the ignition is on.




28-pin connector

We connect 8 wires to the 28-pin connector. Pin 2 is the reverse gear signal and the only connection in the top row. In the bottom row, we connect pin 17 (speed pulse), pins 21 to 23 (steering wheel controls) and pins 26 to 28 (AUX input).

Here are the jumper wires connected to the 28-pin connector (TE Connectivity 1565373-4):



Then wrap the connector in electrical tape to secure the jumper wires. Cut off the 3.5 mm jack from the 3.5 mm to 3 RCA cable (where we got the RCA jack for the rear view camera from). Strip the 3 wires that are connected to the 3.5 mm jack. We are going to connect them to pins 26 to 28. Use a multimeter to determine which wires are connected to which ring on the 3.5 mm connector. Following the description on page 24 of the AVIC-8100NEX installation manual, the wire connected to the tip of the 3.5 mm is the left audio signal, which gets connected to pin 28. The next inner ring (next to the tip) is the right audio signal, which goes to pin 26. Finally, the wire connected to the 3rd ring (ring closer to the cable end of the 3.5 mm jack, but not the connection closest to it) is ground and needs to be connected to pin 27. Please note that with the original 3.5 mm to 3 RCA cable, the meaning of the different connectors on the 3.5 mm jack may be different. This is why it's important that you measure which wire is connected to which part of the 3.5 mm jack and connect it to the appropriate pin on the 28-pin connector.

After connecting the 3.5 mm jack, our wiring harness now looks like this:



Now it's time to connect the steering wheel controls interface to this harness. I got the PAC SWI-RC interface and followed their online instructions for the 2014 Toyota Prius (they don't have the 2015 yet). I had to connect pin 21 to the white wire and pin 22 to the white/black wire. Pin 23 needs to be grounded. Fortunately, PAC SWI-RC comes with two ground wires, which are connected. So I could connect one to pin 23 and the other to ground pin 7 of the 10-pin connector. This took care of grounding pin 23 and also grounding the steering wheel control interface. This means I had to remove the jumper wire I connected to ground earlier that was meant for pin 23.


Putting things together

Now it's time to connect the different harnesses together. Connect the parking brake wire (long, light green wire) of the Pioneer power connector to the wire for the parking brake on the 16-pin connector harness. Also connect the ground and power wires of the steering wheel controls interface to the corresponding wires on the Pioneer power connector (or the daisy chained ground and switched power wires).

Connect the blue wire of the Metra 40-LX11 antenna adapter cable to 12 V switched power. This powers the antenna.

Connect the reverse gear signal wire and speed pulse wire of the 28-pin connector harness to the Pioneer power connector.

In the end it looks like this:



In the lower left corner is the connector that plugs into the steering wheel controls interface module and attached to it is a bundle of cables that are not being used by the steering wheel controls interface. In the middle is the black Pioneer power connector and the 6-pin and 10-pin harnesses connected to it. Below it is the 28-pin connector harness with the 3.5 mm AUX jack and the antenna jack that plugs into the radio. On the right is the 16-pin connector harness with the 12 V to 6 V DC converter. The input power and ground wires of the voltage converter are not connected yet. They will be connected to the two speaker wire leads in the top center of the image, which are the ends of the ground and 12 V switched power daisy chains. The reason why these wires are not connected yet is because they will be spliced together with the power and ground wire of the additional USB port that I installed. But the wires of the USB port needed to be pulled through behind the dash, and so I couldn't connect those wires beforehand.

The whole harness is quote a mess now, but at least it directly plugs into all the factory wiring, which will make installation quite painless. Make sure to bundle as many wires together as you can and wrap them in electrical tape. This will remove tension from the splice points an the wire connectors.


Installation

I read in several places that the AVIC-8100NEX has an issue with glare, since it's a capacitive touchscreen. So I followed this guide and installed an iPad Air anti-glare screen protector.

Follow the Pioneer installation instructions to install the GPS antenna and microphone. Connect the 5 connectors (6-pin, 10-pin, 16-pin, 28-pin, antenna) of the combined harness into the factory wiring. Also connect the Metra AX-TOYUSB USB cable into the factory wiring. Install the additional USB port and connect the ground and switched power wires of the additional USB port and the 12 V to 6 V DC converter to the last link in the ground and 12 V switched power daisy chains. Also, find a secure place to put the steering wheel controls interface module and connect it to the harness. Then program the steering wheel interface according to its manual.

Here's the harness (I'm talking about the big collective harness now) plugged into the factory connectors behind the dash. Pretty messy...



Attach the double DIN brackets and housing (I used the Metra 95-8226B Dash Kit) to the Pioneer radio. Carefully place the radio at the opening in the dash. Now connect all the things to the Pioneer unit: power connector, GPS antenna, radio antenna, microphone, steering wheel controls input, AUX input, rear view camera, and the two USB cables (one from the factory harness with the adapter and one from the additional USB port).

Turn on the ignition and test all the functions (rear view camera, steering wheel controls, speakers, radio, AUX input, USB ports, GPS). If everything works, carefully insert the radio and try to get the wires out of the way. Secure the radio with the for screws, install the last piece of the Metra dash kit and re-assemble the dash.

Here's what it looks like after the installation:






Some General Notes

• It was not necessary to disconnect the 12 V battery (in fact, for testing things and measuring stuff with a multimeter, you need the battery to be connected)
• I wish I had used a longer cable for the RCA jack for the rear view camera
• Use towels or something similar to cover the dash (especially the AC unit and shift lever) when installing the new radio
• If you start the hybrid system while the dash is open (to measure some wires or test the new radio installation, for example), make sure to replace (and connect) the dash piece around the shift lever. If this piece of the dash is not connected to the car, you will get an error message saying there was a problem with the hybrid system. After you plugged in this piece of the dash, the warning will disappear after starting the car 3 times.

What works

• GPS navigation
• Radio
• AUX input
• Both USB ports connected to the Pioneer head unit, 3rd charger USB port
• Steering wheel controls (both left (audio, radio) and right (climate control, TRIP, DISP, not sure yet about Answer Calla and End Call buttons on the steering wheel below the volume buttons. When I programmed the PAC SWI-RC, it clearly recognized those buttons, but the Pioneer unit hasn't reacted to them yet, maybe that's a setting with the head unit
• Screen brightness decreases when I turn on the parking or low beam headlights
• Rear view camera (picture looks good, automatically switches to camera when I go into reverse)
• Speed pulse wire

What DOESN'T works

• Can no longer view the 1-minute consumption graph on the central screen, but this was expected

I hope this post will be useful for people. Please reply if you need more info or have additional information (e.g. about wiring that I didn't test myself).

 

Hi RIKER,

I'm glad this is useful for you. The post is now complete. Please let me know if you have questions or additions.

 

I need to make this post in order to be allowed to post URLs. Silly rule...