According to this. The lower black plug and white plug on main harness plug have nothing to do with the Amp.

small white plug x13598
Pin No. / Wire Color / Function
1 / / No function
2 / White-Brown / Audio common from 6CD player
3-7 / / No connection
8 / White-Red / Audio Left Channel from 6CD player
9 / White-Blue / Audio Right Channel from 6CD player
10 / / No Connection
11 / NAV / TV Audio +
12 / NAV / TV Audio -

NEW Small black plug: x13649 plug
Pin No. / Wire Color / Function
1 / Tape left +
2 / Tape left -
3 / Left Connection for AUX Input
4 / Right Connection for AUX Input
5 / NAV / TV Audio +
6 / White-Black / Phone audio + Positive
7 / Tape right +
8 / Tape right -
9 / No connection
10 / AUX Input Ground
11 / NAV / TV Audio +
12 / Brown-Black / Phone Audio - Groundv

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2004 Gray/Gray 3.0 X5