2005 Mustang factory subwoofer amp use

I have a 2005 Mustang with the Shaker 500 stereo. I pulled out the stereo and installed a Kenwood DDX-7015. I would like to use the factory door subs. They have one amplifier per sub and I have the factory wiring diagram and I hooked up my stereo sub output to the amps, but it didn't work. I also tried using a speaker level input and that didn't work also. It doesn't look like there is a switch to turn the amps on/off, it looks like they always have 12V going to them. The only other input is a mute line, I assume this is open until you tie it to ground. What input do these amps want?

Thanks a lot, I have been messing with this for a while and it worked great!! I used a 465 ohms resistor with the External amplifier control wire. I have no loud pop when I turned this on and it sounds excellent. Everyone kept telling me to just buy an amp and new speakers, but this sounds good enough to me. Also, thanks for the quick response.