Adding my setup here as well since this was another thread i was following as I researched my options and troubleshooting my issues. I hope it helps someone.
Parts list :
Alpine MRV-M500 Mono V-Power Digital Amplifier https://www.amazon.com/dp/B00BMR7UPS..._SclOybASP0N6E
Rockford Fosgate R2S-1X10 Prime R2S Single 10-Inch Shallow Loaded Enclosure https://www.amazon.com/dp/B0068XYNH4..._IEimCZgK7Qtg1
Kicker CK4 Complete 4 Gauge OFC CK-Series 2-Channel Amplifier Installation Kit https://www.amazon.com/dp/B00IFA1HDQ..._1dlOybDEJFDVN
Kicker KISLOC 2-Channel K-Series Speaker Cable to RCA Adapter with Line Out Converter https://www.amazon.com/dp/B00I4EF1BC..._hclOybXMQBJ9E
Alpine RUX-**** Remote Bass Level Control **** for PDX-M12 and PDX-M6 https://www.amazon.com/dp/B003KEGS90..._wQJCUslDK9gnB
ATR add a circuit 2-10a
Did not use /returned :
ScanTool 426101 OBDLink MX Bluetooth: Professional OBD-II Scan Tool for Android & Windows https://www.amazon.com/dp/B006NZTZLQ..._x-kOybAEH389X
Motorcraft WPT1212 Multi-Function Switch Connector Assembly https://www.amazon.com/dp/B009B5SPHU..._AblOyb4D00ZRQ
-Wires power from battery through passenger side gromet. Pita to feed through gromet.
-ground to existing bolt next to rear seat bracket. Sanded paint off for better connection.
-Remote wire tapped into fuse #23 via ATR add a circuit in passenger kick panel
-tapped into BOTH rear speaker wires in BOTH b pillars. They are the pairs that are intertwined.
White w green stripe (+)
Brown W yellow stripe (-)
Brown W white stripe (+)
Brown w blue stripe (-)
-ran the tapped wires into each of the Kicker line out converter wires. Also grounded the brown wire to same spot where I grounded the amp ground
-cut wall carpet so sub can fit better behind seat
-I have sub slightly tilted for now. Will need to cut center bolt and perhaps add 2x4 or something. Currently resting next to bolt closest to outside of truck, while other sids rest on top of bolt closer to center of truck. This gives enough clearance since part of sub is sitting lower and top of box is narrower.
I hope that makes sense and helps out others. I had read several posts /threads where people were experiencing same problems. I could not get the wpt 1212 to sub factory harness method working for the life of me. I was even thinking of tapping directly into factory sub harness wires (skipping wpt 1212 harness) instead of b pillars but just didn't feel like going though that trouble since I could not determine what was not working initially (1212 harness, factory sub, forscan settings). In hindsight, I would have gone this route from beginning (tapping to bpillar speaker wires).