How to Identify Subwoofer Pos/Neg/On with a Multimeter?

I'm trying to replace a factory stereo in a 2008 Ford Escape with a Sony XAV-AX1000 stereo. The factory stereo came w/ a factory subwoofer & amp. The factory harness has two plugs, one with 24 pins and another with 16 pins. I bought a wiring harness on Amazon that's supposed to work, but only the big plug fits, and the small one is the wrong size. The small jack in the harness has 6 pins, which are supposed to be: woofer + woofer - subwoofer + subwoofer - woofer amp on/off subwoofer amp on/off The small factory plug has only 6 pins wired, plus 1 additional bare wire, out of 16 total possible pins. I assume the bare wire is ground to chassis. But I don't know what the other six pins are wired to. I presume (hope) one is the subwoofer amp on/off wire, and at least two others are subwoofer pos/neg wires. How can I figure out which is which? Is there an easy way to use a multimeter to tell if a wire goes to turn an amp on/off? I could obviously try to listen for the subwoofer to work, but that means I have to get 3 out of the 6 wires connected correctly. (If my math is correct, there are 90 combinations to try--too many). Thanks! --------> aha! <--------- Just writing this out and stewing on it made me realize... I could plug in the big plug, turn on the radio, and check the voltage on the pins on the small plug to see which ones jump to 12v. Those would be the subwoofer & woofer on/off wires. That would leave 4 wires to check by trial and error to see which ones are subwoofer pos/neg wires. I hope I'm right...

you really cant with a multimeter. You can take a 5v battery or a phase tester and pop the speaker. Phase tester will tell you if it in phase or not but you have to hold it close to the speaker for a accurate reading. The 5v battery test you have to watch which way the cone goes. If it goes out you are in phase (good), if it goes in you are out of phase (bad). Dont use a 12v or higher battery just incase you test the wrong wire and fry a bcm or set off a air bag. Just make sure the amp is powered on before testing them violet/green + pin 1 green/white - pin 2 both are at the deck and go out to the amp, can just add a cut off rca end to the wires to get audio to the amp. no wires colors shown for amp to sub33 years as a installer now just a retired old guy. Favorite thing to install/topic are remote starts/car alarms. Stop using test lights!!!