An in-vehicle electronic audio and navigation system comprising: an in-vehicle electronic audio apparatus mounted in a vehicle; and a portable electronic navigation apparatus detachably provided to the in-vehicle electronic audio apparatus, wherein: the in-vehicle electronic audio apparatus comprises: a detecting portion configured to detect connection of the portable electronic navigation apparatus; and a first controller configured to determine whether or not the portable electronic navigation apparatus is powered on, when the connection of the portable electronic navigation apparatus to the in-vehicle audio apparatus is detected by the detecting portion, and configured to activate the portable electronic navigation apparatus and to request the portable electronic navigation apparatus to display a navigation screen of the portable electronic navigation apparatus on a display portion of the portable electronic navigation apparatus, when the first controller determines that the portable electronic navigation apparatus is not powered on. an in-vehicle electronic audio apparatus mounted in a vehicle; and a portable electronic navigation apparatus detachably provided to the in-vehicle electronic audio apparatus, wherein: the in-vehicle electronic audio apparatus comprises: a detecting portion configured to detect connection of the portable electronic navigation apparatus; and a first controller configured to determine whether or not the portable electronic navigation apparatus is powered on, when the connection of the portable electronic navigation apparatus to the in-vehicle audio apparatus is detected by the detecting portion, and configured to activate the portable electronic navigation apparatus and to request the portable electronic navigation apparatus to display a navigation screen of the portable electronic navigation apparatus on a display portion of the portable electronic navigation apparatus, when the first controller determines that the portable electronic navigation apparatus is not powered on. the in-vehicle electronic audio apparatus comprises: a detecting portion configured to detect connection of the portable electronic navigation apparatus; and a first controller configured to determine whether or not the portable electronic navigation apparatus is powered on, when the connection of the portable electronic navigation apparatus to the in-vehicle audio apparatus is detected by the detecting portion, and configured to activate the portable electronic navigation apparatus and to request the portable electronic navigation apparatus to display a navigation screen of the portable electronic navigation apparatus on a display portion of the portable electronic navigation apparatus, when the first controller determines that the portable electronic navigation apparatus is not powered on. a detecting portion configured to detect connection of the portable electronic navigation apparatus; and a first controller configured to determine whether or not the portable electronic navigation apparatus is powered on, when the connection of the portable electronic navigation apparatus to the in-vehicle audio apparatus is detected by the detecting portion, and configured to activate the portable electronic navigation apparatus and to request the portable electronic navigation apparatus to display a navigation screen of the portable electronic navigation apparatus on a display portion of the portable electronic navigation apparatus, when the first controller determines that the portable electronic navigation apparatus is not powered on.