I bit the bullet and replaced the factory headunit in my 2017 Forester XT without nav, with HK.
For the longest time, if we wanted to replace the factory headunit, we would also have to replace the factory HK amp.
Here’s my detail on replacing the factory unit while retaining the factory amp.
Items purchased:
- Pioneer AVIC-W8400NEX Navigation Receiver
- iDatalink Maestro ADS-MRR Universal Radio Replacement & SWI
- iDatalink HRN-RR-SU2 Install Harness for select Subaru models
- Scosche SU2031B Subaru Kit 15-up Impreza/XV Crosstrek, DD, Black
- Toyota & Lexus antenna adapter 09-Up Toyota/Lexus
- SiriusXM SXV300
- USB 3.0 Mount Cable - Powerbeast Dual USB 3.0 Extension USB Mount,Dash Mount,Flush Mount
Additional items used:
- Solder gun
- Solder
- Shrink tube
- Tessa tape
- Electric tape
- Ratchet, a couple extensions, 10MM(magnetic if possible)
- Working light, it’s dark
- Computer with account to Idatalink for programing the Maestro module.
First item of business, research. I took my time selecting the right new radio and what items I may need for the install. I also read a lot of instructions.
Wiring
This is where I merged the two Maestro wiring harnesses with the Pioneer harness. The SU2 harness comes with a few different adaptors and you’ll need to find what adaptors you’ll need for your car model and features.
Below are some picture of merging the harnesses together and some prelayouts. I used Tessa tape afterwards



Radio removal
There are a few good videos on how to remove the factory radio on YouTube. A simple 2017 WRX radio removal will get you a few different ones. There are a few different methods to getting the bolts unbolted from the side. For the passenger side, you just have to remove the glove box. No tools required. The bolt will require and 10MM and a couple extensions. I don’t have a magnetic socket, so I just taped a magnet to the socket. For the drivers side, I just removed the small panel beside the console. I believe it was a small screw on the bottom and a couple tugs to remove it. It’s a little hard to see the bolt, that’s where the extensions and magnetic socket work.
Use a pry tool to remove the top vent. I spent 5 bucks and got a trim removal set off Amazon. Best 5 dollar purchase.
As you start to pry off the vent, you may want to use a trim tool or screwdriver to push the tabs on the two electrical plugs you’ll have to remove.
As you pull that vent off, the radio and AC/heater controls all come off together. There are a lot of plugs on the back of the radio. Don’t forget to reinstall that AC/heater controls on the Scosche trim panel. Don’t forget to remove the starlink module and put it back in. It’s like a puzzle, but it will fit back in. See picture below. If you don’t plug all the harnesses back in, your Starlink will not work and neither will your front speakers. My trick was putting it in vertical and then laying it sideways once it was back in there.
The pink wire below is the starlink wire that has to be tapped.

Below is the finished install.I also put the dual usb port in where the 12 volt power plug went. It’s a simple removal of the 12 plug from the back in push the usb plug in. I was able to attach them to usb 1 and usb 2 on back on the unit.

Don’t forget to route the mic to your liking. I routed mine to the side of the rearview mirror.
When used with the Meastro RR, you’ll have gauges you can display.

There’s also a TPMS sceen.

OK, I've had the radio in for a few weeks and here's some of my latest comments.
1. The radio signal is horrible, granted I hardly use it. I believe I know how to fix it. Pioneer doesn't have a power antenna wire. Initially I planned and tried to solder the car side blue wire(antenna power) to the red accessory wire. I kept blowing the idatalink wiring harness fuses. After I did some testing and digging, I removed that wire from the accessory wire and the radio will work. Idatalink told me that there's another blue wire in the 6 pin harness that needs to be cut. From what I gather, that wire is grounded in that harness as it fits other cars too. I'm told if I cut the 6 pin blue wire, I can wire the blue wire in the 20 pin back to the accessory to have better radio reception.
2. I'm still working out the Sirius radio details. I've been lagging here. I'm not in a big hurry as I have the siriusXM app that holds me over. I might get a Toyota adaptor to hook up to the blue SiriusXM satilite antenna. I've read a few confirmations on that it will work.
3. My GPS speed on the navigation is off, unless I drive it at what it says. IE.. driving 48 while displaying 48.While the idatalink gauges are correct, they read from the OBD port, the GPS speed doesn't match the signal speed vss that's going into the unit.I do have to say that I'm getting great GPS signal. Idatalink blames the unit and Pioneer is blaming IdataLink. sounds fun right! Pioneer said I could try to cut the VSS wire to the unit and let the GPS do all the speed calculations. I feel I shouldn't have to do that, but I may have to try when I fix the other things. It's cold out and the carplay works enough to not care about regular radio.
4. Wireless Carplay is what this car should have came with. It's such a huge improvement so far. I enjoy using Waze for navigation and Pandora or Amazon for music.
5. The sound has improved so much on top of already having the HK system.
For the longest time, if we wanted to replace the factory headunit, we would also have to replace the factory HK amp.
Here’s my detail on replacing the factory unit while retaining the factory amp.
Items purchased:
- Pioneer AVIC-W8400NEX Navigation Receiver
- iDatalink Maestro ADS-MRR Universal Radio Replacement & SWI
- iDatalink HRN-RR-SU2 Install Harness for select Subaru models
- Scosche SU2031B Subaru Kit 15-up Impreza/XV Crosstrek, DD, Black
- Toyota & Lexus antenna adapter 09-Up Toyota/Lexus
- SiriusXM SXV300
- USB 3.0 Mount Cable - Powerbeast Dual USB 3.0 Extension USB Mount,Dash Mount,Flush Mount
Additional items used:
- Solder gun
- Solder
- Shrink tube
- Tessa tape
- Electric tape
- Ratchet, a couple extensions, 10MM(magnetic if possible)
- Working light, it’s dark
- Computer with account to Idatalink for programing the Maestro module.
First item of business, research. I took my time selecting the right new radio and what items I may need for the install. I also read a lot of instructions.
Wiring
This is where I merged the two Maestro wiring harnesses with the Pioneer harness. The SU2 harness comes with a few different adaptors and you’ll need to find what adaptors you’ll need for your car model and features.
Below are some picture of merging the harnesses together and some prelayouts. I used Tessa tape afterwards



Radio removal
There are a few good videos on how to remove the factory radio on YouTube. A simple 2017 WRX radio removal will get you a few different ones. There are a few different methods to getting the bolts unbolted from the side. For the passenger side, you just have to remove the glove box. No tools required. The bolt will require and 10MM and a couple extensions. I don’t have a magnetic socket, so I just taped a magnet to the socket. For the drivers side, I just removed the small panel beside the console. I believe it was a small screw on the bottom and a couple tugs to remove it. It’s a little hard to see the bolt, that’s where the extensions and magnetic socket work.
Use a pry tool to remove the top vent. I spent 5 bucks and got a trim removal set off Amazon. Best 5 dollar purchase.

As you start to pry off the vent, you may want to use a trim tool or screwdriver to push the tabs on the two electrical plugs you’ll have to remove.
As you pull that vent off, the radio and AC/heater controls all come off together. There are a lot of plugs on the back of the radio. Don’t forget to reinstall that AC/heater controls on the Scosche trim panel. Don’t forget to remove the starlink module and put it back in. It’s like a puzzle, but it will fit back in. See picture below. If you don’t plug all the harnesses back in, your Starlink will not work and neither will your front speakers. My trick was putting it in vertical and then laying it sideways once it was back in there.

The pink wire below is the starlink wire that has to be tapped.

Below is the finished install.I also put the dual usb port in where the 12 volt power plug went. It’s a simple removal of the 12 plug from the back in push the usb plug in. I was able to attach them to usb 1 and usb 2 on back on the unit.

Don’t forget to route the mic to your liking. I routed mine to the side of the rearview mirror.
When used with the Meastro RR, you’ll have gauges you can display.

There’s also a TPMS sceen.

OK, I've had the radio in for a few weeks and here's some of my latest comments.
1. The radio signal is horrible, granted I hardly use it. I believe I know how to fix it. Pioneer doesn't have a power antenna wire. Initially I planned and tried to solder the car side blue wire(antenna power) to the red accessory wire. I kept blowing the idatalink wiring harness fuses. After I did some testing and digging, I removed that wire from the accessory wire and the radio will work. Idatalink told me that there's another blue wire in the 6 pin harness that needs to be cut. From what I gather, that wire is grounded in that harness as it fits other cars too. I'm told if I cut the 6 pin blue wire, I can wire the blue wire in the 20 pin back to the accessory to have better radio reception.
2. I'm still working out the Sirius radio details. I've been lagging here. I'm not in a big hurry as I have the siriusXM app that holds me over. I might get a Toyota adaptor to hook up to the blue SiriusXM satilite antenna. I've read a few confirmations on that it will work.
3. My GPS speed on the navigation is off, unless I drive it at what it says. IE.. driving 48 while displaying 48.While the idatalink gauges are correct, they read from the OBD port, the GPS speed doesn't match the signal speed vss that's going into the unit.I do have to say that I'm getting great GPS signal. Idatalink blames the unit and Pioneer is blaming IdataLink. sounds fun right! Pioneer said I could try to cut the VSS wire to the unit and let the GPS do all the speed calculations. I feel I shouldn't have to do that, but I may have to try when I fix the other things. It's cold out and the carplay works enough to not care about regular radio.
4. Wireless Carplay is what this car should have came with. It's such a huge improvement so far. I enjoy using Waze for navigation and Pandora or Amazon for music.
5. The sound has improved so much on top of already having the HK system.