i just finished installing sony cd player into truck and sound doesnt work?

i have an ipod interface that uses 2 audio plugs and the sound works when i plug them in but there is no way to turn the sound up and down when the colume dial is turned. it only comes in on one volume setting if i turn it down it turns off. what should i do to to make the car audio system play with the cd player. i plugged in all of connecting wires

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