if your nav screen does not show telephone, either your module is a TCU, just a telematics that ran out of subscription, or the BT unit is not communicating on the ibus - once powered, it should tell the ibus that it is present, by transmitting the module ID (priority level ID)... assuming that you have a BT, you should start checking the fuses to see if the module is powered up... then, check the cables, to see if any of the wires is cut, shorted, chaffed, especially the power and the ibus wires...

start small, check the fuses...