System Description
AUDIO SYSTEMAn audio system is standard factory-installed equipment on this model. The standard equipment audio system includes an AM/FM/cassette (RBB sales code) radio receiver, and speakers in six locations. Several combinations of radio receivers and speaker systems are offered as optional equipment on this model. The audio system uses an ignition switched control of battery current so that the system will only operate when the ignition switch is in the ON or Accessory positions.
A Compact Disc (CD) changer with a ten disc magazine, remote radio switches with six functions mounted to the backs of the steering wheel spokes, and a memory system that automatically stores and recalls up to twenty radio station presets (ten AM and ten FM) and the last station listened to for two drivers are optional factory-installed equipment on this model. Refer to Electrical, Power Seats for more information on the memory system.
The audio system includes the following components:
- Antenna
- Compact disc changer (available with RBP sales code radio receivers only)
- Power amplifier (with premium speaker system only)
- Radio noise suppression components
- Radio receiver
- Remote radio switches
- Speakers
Certain functions and features of the audio system rely upon resources shared with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) data bus network. The PCI data bus network allows the sharing of sensor information. This helps to reduce wire harness complexity, internal controller hardware, and component sensor current loads. At the same time, this system provides increased reliability, enhanced diagnostics, and allows the addition of many new feature capabilities. For diagnosis of these electronic modules or of the PCI data bus network, the use of a DRB scan tool and the proper Diagnostic Procedures are recommended.
The other electronic modules that may affect audio system operation are as follows:
- Body Control Module (BCM) - (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/BODY CONTROL/CENTRAL TIMER MODULE - DESCRIPTION) for more information.
- Driver Door Module (DDM) (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/DRIVER DOOR MODULE - DESCRIPTION) for more information.
- Passenger Door Module (PDM) (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/DRIVER DOOR MODULE - DESCRIPTION) for more information.
The audio system includes the following major components, which are described in further detail elsewhere in this service information:
- Amplifier - On models equipped with the optional premium speaker system, an audio power amplifier is located on the rear floor panel underneath the right end of the rear seat cushion in the passenger compartment.
- Antenna Body and Cable - The most visible component of the antenna body and cable are the antenna adapter and the antenna cap nut, which are located on the top of the right front fender panel of the vehicle, near the right end of the cowl plenum.
- Antenna Mast - The antenna mast is a metal rod that extends upward from the antenna body and cable on the top of the right front fender panel of the vehicle, near the right end of the cowl plenum.
- Radio - The radio for this model is located in the instrument panel center stack area, inboard of the instrument cluster and above the heater and air conditioner controls.
- Radio Noise Suppression Ground Strap - A radio noise suppression ground strap is installed between the rear of the engine cylinder head(s) and the dash panel sheet metal in the engine compartment.
- Speaker - The standard speaker system includes six speakers in six locations, while the premium speaker system includes an amplifier for the six speakers in six locations.
Hard wired circuitry connects the audio system components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the audio system components through the use of a combination of soldered splices, splice block connectors and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information for complete standard and premium audio system circuit diagrams. The wiring information includes proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices, and grounds.
The audio system components are designed to provide audio entertainment and information through the reception, tuning and amplification of locally broadcast radio signals in both the Amplitude Modulating (AM) and Frequency Modulating (FM) commercial frequency ranges. Electromagnetic radio signals that are broadcast from a radio station induce electrical modulations into the audio system antenna mast. The antenna body and cable conduct these weak signals from the antenna mast to the radio. The radio then tunes and amplifies these weak radio frequency signals into stronger electrical audio signals that are required in order to operate the audio system speakers. The speakers convert these electrical signals into air movement, which reproduces the sounds being broadcast by the radio station.
Some audio systems also offer the user the option of selecting from and listening to prerecorded audio cassette tapes, audio compact discs, or both. Regardless of the media type, the audio system components provide the user with the ability to electronically amplify and adjust the audio signals being reproduced by the speakers within the vehicle to suit the preferences of the vehicle occupants.
The audio system components operate on battery current received through a fuse in the Junction Block (JB) on a fused ignition switch output (run-acc) circuit so that the system will only operate when the ignition switch is in the ON or Accessory positions.
On vehicles that are equipped with the optional remote radio switches, the BCM receives hard wired resistor multiplexed inputs from the remote radio switches. The programming in the BCM allows it to process those inputs and send the proper messages to the radio receiver over the PCI data bus to control the radio volume up or down, station seek up or down, preset station advance, and mode advance functions.
On vehicles equipped with the optional memory system, when the DDM receives a Driver 1 or Driver 2 memory recall input from the memory switch on the driver side front door trim panel or a memory recall message from the Remote Keyless Entry (RKE) receiver in the PDM, the DDM sends a memory recall message back to the radio receiver over the PCI data bus to recall the radio station presets and last station listened to information.
The PCI Bus inputs into the radio are used for VF dimming and remote steering wheel controls. All the radios are capable of displaying faults and allowing certain actuation tests through the use of the DRB III. When attempting to perform PCI Bus diagnostics, the first step is to identify the radio in use in the vehicle.
When trouble shooting 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.
Remote Radio Controls
These radios can be controlled via remote radio switches (optional). These switches are located on the back side of the steering wheel. They control mode, preset, seek up, seek down, volume up and volume down functions.
These functions are inputs to the Body Control Module and can be read with the DRB III. The switches are a multiplexed signal to the BCM. The radio control MUX circuit is a 5 volt line that is pulled to ground through different value resistors built into the switches. This causes a voltage drop to be seen by the BCM and it sends a specific message to the radio on the PCI Bus circuit. The radio then responses to the message.
This circuit is fairly simple to troubleshoot. The circuit must be complete from the switches in the steering wheel to the BCM. The ground must be complete so that the switches can cause the voltage drop for the BCM to see. The circuit passes through the clockspring so continuity through this devise must be verified.