PAC OS-2C-CTS OnStar Interface for 2003-2007 Cadillac CTS and 2004-2007 Cadillac SRX Vehicles: * Plug and play — no cutting or splicing into factory plug * Communicates directly with OnStar module to prevent false triggering and eliminating unwanted audio noise * On-board amp will drive two 4W speakers in stereo * Use with existing factory speakers or external speakers * For 2003-2007 Cadillac CTS and 2004-2007 Cadillac SRX vehicles * Includes chime module