i just did this and it didnt work.....i will double check later today after work but did you ever do this yourself? also.....how would you go about getting a signal for an aub amp if that way doesnt work....

here is the instructions again if you need to refer to them....

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There isn't any rca outputs on the TL's Stock headunit. You need to tap into the wires for your amps input. The Stock sub amp is behind the rear seat on the passenger side. First remove the bottom part of the seat. It's only held on by one bolt near the middle toward the driver's side. Then there is one bolt on each side holding the rest of the seat to the car. Take those off and romove the back seat. Now you see the small little thing called the BOSE AMP. There is two bolts to it. After you removed the amp you can unplug the wire harness from it. From there you need to cut bout an inch or so ( the black sheilding holding all the wires together) to give you some room to do the wire tapping. After cutting the sheilding and pulling it up some, you will see a brown coated twisted pair of wires. That is what you are going to tap with speak wire with an rca at the other end. You can pick one up at any electronic store like Radio Shack. Also pick up some wire taps for an easier install. It seems it doesn't really matter how you connect the rca wire to the brown wires (Meaning the +/-). You need three wire taps. With the first wire tap, tap one of the brown wires, then the other wire tap, tap the other brown wire. That's it for the Sub input to your amp. Now to tap the remote wire so that your aftermarket amp will turn on with the HU. In the stock amp wiring harness you will see a blue wire. That's the romote to turn on your amp. tap that one. Other then that you need to run a power wire from the battery to your amp in the trunk. In the trunk you can ground the amp to the chassis by the white earring thingy hook in the driver's side. That's it, put the back seat back together and now it's time to have some fun with for your new bass.

THANKS AGAIN

 

Nope, I have never used this method...I know several people who have though. I usually go from under the rear door sils to get a left and right channel input from the rear speaker outputs.