Pioneer deh-p6700, amp turn on wire

I had a pioneer deh-p6700 installed, professionaly in my 04 malibu I am now adding an amp and i cant determine which wire is neededfor my amp my blue/white wire is being used, its tied into my factory harness to a solid blue wire?.. and for some reason when i apply the test light..nothing.

The blue/white wire coming out of your deck is the wire needed to turn on your amp. it maybe connected to the blue wire on your wire harness a: used to control a existing amp b: used for a auto-antenna relay control c: installer may have just connected it in case you did decide to add an amp. The only time this wire should have any voltage is when the pioneer deck is on, not when the car is off. i hope this helps.

it does.i needed to know if the wire was used for anything else.ill ad my amp wire to them. thanks