Radio, Stereo, and Compact Disc: Description and Operation

AUDIO SYSTEM
The factory installed radio receiver communicates on the Programmable Communication Interface (PCI) data bus network. This is used for the remote radio switches that are mounted to the steering wheel, and also used for radio diagnosis with the DRB III.

The remote radio switches are resistor multiplexed units that are hard wired to the CTM through the clockspring. The CTM monitors the status of the remote radio switches and sends the proper switch status messages on the PCI data bus network to the radio receiver. The electronic circuitry within the radio is programmed to respond to these remote radio switch status messages by adjusting the radio settings as requested.

When troubleshooting output shorts or "output" error messages, the following applies:

On radios without an external amplifier, the term "output" refers to the path between the radio and the speaker. This type of circuit can be monitored all the way through the speaker connections by the radio assembly. When the radio displays a shorted output DTC with this type of system, the speaker, radio or wiring could be at fault.

On radios with an external amplifier, the term "output" refers to the circuit between the radio connector and the amplifier. The radio is capable of monitoring only this portion and can tell nothing about the circuit between the amplifier and the speakers. Consequently, a shorted output DTC on this type of system would only refer to this circuit. A faulty speaker could not cause this DTC.

AMPLIFIER (PREMIUM SYSTEM)
The Premium Audio Amplifier uses a microprocessor for audio digital signal processing (DSP) and system diagnostics. DSP provides a more accurate and consistent match of the audio system equalization to the vehicle interior. The '03 AN/AN84 Dakota amplifier has four channels for superior sound quality.

The amplifier reads the VIN from the PCI bus and sets itself to match the vehicle. The amplifier will send four beeps to the vehicle speakers at ignition on, if it does not read the VIN correctly. A replacement amplifier may beep at the first power up, but if these beeps are heard after the first ignition on, the DRB III should be used to verify the amplifier is connected to the PCI bus and that the VIN on the PCI bus is correct.

The amplifier, wiring to the speakers and the speakers work independently from the radio. The amplifier's microprocessor supports several diagnostic functions. Tests can be run from the DRB III that will help in diagnosing audio system problems. The DRB III can display fault messages when an input or output problem to the amplifier is detected. The amplifier can detect wiring shorts and suggest which wires are likely to be shorted. The amplifier can send test signals that can be used to verify that the amplifier, speakers, and wiring to the speakers are operating properly. The amplifier can also be used to test if the radio is sending audio signals to it. The DRB III can be used to verify the amplifier equalization setting matches the vehicle, in case there is a sound quality complaint. Using the DRB III audio system diagnostics can determine the nature of the problem.

Diagnostic test the Amplifier can perform through the DRB III:
- Continuous Tone Test - This test will send a continuous tone to each speaker and will verify the integrity of an individual channel.

- PCI Amplifier Test - This test will detect a PCI bus or checksum failure.

- Input Test - This test will detect the activity on the amplifiers input channels from the radio.

- Speaker Output Test - This test will detect the activity on the amplifiers output channels to the speakers.