Principles of Operation

WARNING: This page is about a different car, the 2003 Ford Thunderbird. However, it is still accessible from the selected car via links, so may be relevant.

When the audio unit is powered up a wake-up signal is sent to the subwoofer amplifier. Audio output signals are then sent continuously to the subwoofer amplifier and center imaging amplifier. These signals are then amplified and sent to the speakers as a fluctuating AC voltage, thus producing sound from the speakers. A fluctuating AC voltage audio signal is also sent to the remaining speakers, directly from the audio unit, to produce sound. The steering wheel controls are a multiplexed system that use different resistor values to produce different voltage levels on a single circuit. Each button that is pressed results in a unique voltage signal at the audio unit. This voltage signal is then interpreted by the audio unit as a distinct command. The audio unit is linked to the SCP network and therefore, trouble codes can be obtained with a diagnostic tool. The audio unit also has a self diagnostic mode that can be entered by pressing preset buttons 3 and 6 simultaneously.