‘18 SCrew XL STX: no 12v for stock sub install
 

Tried to install a stock sub. It did not come with a manual, but it came with the stock wiring connector and mounting hardware. Activated forscan codes for sub on aux1 and six-speaker with kicker. I plugged the sub connector into the molex in the back left corner of the cab, but am not getting any voltage on the fat black and red wires in the bundle. The other three wires are remote and signal pos/neg and are very small, so it’s not a case of mistaken wires. I checked the main fuse box and the “audio amplifier” 20a fuse in slot 22 is not present, nor are there any clips in slot 22 to accept a fuse. Is the required wiring not present on an XL—STX with Sync3/CD/Sirius? I’ve had two dealers say it ahould install. Those if you with a stock sub, do you have a fuse on slot 22? Also, has anybody else done this with a STX?

The stock Sony sub? Stock kicker sub? Which one? Does the enclosure have the oem amp mounted to it?

the rear plug behind the back seat if this is what you are referring to is disabled for the XL.. you have to tap into the front or rear door speakers .. also the power is not 12v .. i tried to use the remote turn on lead and it was 5v

edit: and when i say disabled.. nothing you do in forscan will let the harness work

Result
 

Hey everybody, thanks for the help! I ended up installing a Rockville RW10CA. If I’m going to run my own power, I might as well save $450 over OEM and have a sub with adjustable low pass/gain/bass boost curve. And, for half the price of a Kicker Hideaway, I think this delivers a much better value. I also tried to fit the Dual TBX10A, as it was on special at Walmart for $50, but it’s too thick when the seats fold up and the seatback moves toward the back wall.
Install: Buy a 20-ft power wire. Run the wire over the motor, between the firewall and the panel in front of it. The passenger side of the firewall panel can be loosened enough to get the wire fed through. Drill through the existing huge rubber grommet on the left side of the firewall, from the driver footwell. It is dual-layer. Be sure to give the existing wire bundle plenty of space. It would suck to hit that with a drill bit.
The wiring diagram attached to this thread is correct. As soon as you enable external speaker or external subwoofer in Forscan, you will get 6v turn-on signal. This works for the RW10CA, no 12v relay required. I chose external speaker to get a full-range signal with less DSP interference. I did not change the speaker config to 6+kicker, as i want the bass in the speakers, because I’m using speaker signal to feed my sub. I chopped a single RCA video cable in half, then stripped it. I pulled all the woven shielding to one side and twisted it together. I attached this to the low signal negaitve (green). I stripped the core of the wire to reveal the solid copper core. I connected that to the purple, then plugged the RCA into one of the inputs. Works nicely. I ended up cutting the harness because my WPT1212 didn’t show up in the mail before I leave town.

ahhh its Sirus that does it.. I still have my WPT1212 in my truck.. i never removed it after i couldn't get the audio signal to work