For 1990-2009 cars

The entertainment system on this vehicle may have several different configurations available to it. To determine the specific configuration of the vehicle, please see the Service Parts ID Label, and refer to RPO Code List.

Each item in the list below represents topics covered in detail below.

• | Radio Circuit Operation

• | Antenna System

• | AM/FM Reception

• | Speaker Operation

• | Radio Data System (RDS)

• | Radio Data System (RDS) Messages

• | MP3/CD Formatting Information for MP3/CD Radios (If equipped)

• | Integral Multi Disc CD Changer (IMDX)

• | Theft Deterrent

• | OnStar®

• | Speed-Dependant Volume Control (SDVC)

• | Steering Wheel Controls

### Radio Circuit Operation

#### Radio Power

The radio is supplied power by a fused B+ circuit. The radio also utilizes an integral fuse in the path on main battery power. This fuse is located on the radio under the harness connector. The radio does not use a discrete ignition feed circuit for power moding. The power mode master (PMM) provides the system power mode to the radio via serial data messages. The PMM determines the system power mode by processing power mode information from ignition switch inputs. Serial data power modes supported by the radio are OFF, ACCESSORY, RUN, and CRANK REQUEST.

#### Radio Grounds

The vehicle harness provides a ground for the radio circuits. The radio may also be case grounded.

#### Radio Data Link Communication

The radio communicates with other modules via serial data.

#### Radio Outputs

At minimum volume, the plus (+) and minus (-) speaker outputs are approximately half battery voltage, measured to vehicle ground. As the volume increases, the plus and minus change to create a voltage difference between each other, driving the voice coil of the speaker.

### Antenna System

#### Fixed Mast Antenna

The fixed mast antenna can withstand most car washes without being damaged. If the mast should ever become slightly bent, straighten it out by hand. If the mast is badly bent, replace it.

Check occasionally to make sure the mast is still tightened to its base. If tightening is required, tighten by hand.

### AM/FM Reception

#### Radio Signal

The radio signal is sent from a broadcast station and is then received by an antenna. The strength of the signal received depends on the following:

• | The power output (wattage) of the broadcasting station

• | The location of the vehicle (or receiver) relative to the broadcast tower.

• | Obstacles between the tower and the receiver

• | Atmospheric conditions

• | What band (AM or FM) the station is broadcasting

• | Type of antenna and the ground plane

#### AM Reception

The AM band has a lower frequency range than the FM band. These longer wavelengths:

• | Bend around Obstacles

• | Follow the curvature of the earth

• | May reflect off the ionosphere (skip)

The AM frequencies have longer range due to the ground wave. The ground wave follows the curvature of the earth and is effected by its conductivity. Greater conductivity equates to less signal loss thus transmission over water is better than over land. The AM band has a range of 80-320 km (50-200 miles).

#### FM Reception

The shorter wavelengths of the higher frequency FM band:

• | Reflect off obstacles

• | Are absorbed by the ground

• | Penetrate the ionosphere

Broadcasts in the FM band are limited to line of sight reception which is typically 40 km (25 miles). Even when out of a direct line of sight, the signal may be reflected into areas that would be in a shadow otherwise. Factors which affect the line of sight include:

• | Height of the broadcast antenna

• | Height of the receiving antenna

• | Terrain and buildings in the broadcast path

### Speaker Operation

Speakers turn electrical energy into mechanical energy to move air, using a permanent magnet and an electromagnet. The electromagnet is energized when the radio or amplifier (if equipped) delivers current to the voice coil on the speaker. The voice coil will form a north and south pole that will cause the voice coil and the speaker cone to move in relation to the permanent magnet. The current delivered to the speaker is rapidly changing alternating current (A/C). This causes the speaker cone to move in two directions producing sound. When the speaker is at rest, such as when the volume at a minimum value, the voltage applied to each side of the speaker is ½ ignition system voltage. This way, the speaker cone can be moved in either direction.

### Radio Data System (RDS) (If equipped)

The radio may be equipped with the Radio Data System (RDS). The RDS feature is available only on FM stations that broadcast RDS information. This system relies upon receiving specific information from these stations and only works when the information is available. While the radio is tuned to an FM-RDS station, the station name or call letters display.

RDS data is carried in what is known as a "subcarrier". A subcarrier is a frequency that the FM broadcaster is authorized to use to send data that is not audible in the main audio program.

• | RDS functions will only work with FM broadcast stations that are broadcasting RDS data.

• | Not all FM Broadcast stations broadcast RDS data or offer all of the RDS services.

• | The information displayed is dependent upon the information broadcast by the particular station. The information may vary greatly between stations.

• | RDS functions may not work properly when reception is weak, reception is of poor quality, or RDS is not implemented properly by the FM Broadcaster.

• | In some cases, a radio station broadcasting incorrect information may cause the RDS features of the radio to appear to work improperly.

With RDS, the radio can do the following:

• | Seek to stations broadcasting the selected type of programming

• | Receive announcements concerning local and national emergencies

• | Display messages from radio stations

RDS may display text information such as:

• | The name of the station.

• | The type of program.

• | General information such as artist and song title, call in phone numbers, etc.

### RDS Messages

• | ALERT!: Alert warns of local or national emergencies. When an alert announcement comes on the current radio station, ALERT! displays. You will hear the announcement, even if the volume is low or a CD is playing. If a CD is playing, play stops during the announcement. Alert announcements cannot be turned off. ALERT! is not affected by tests of the emergency broadcast system. This feature is not supported by all RDS stations.

• | INFO (Information): If the current station has a message, the information symbol or INFO displays. Press this button to see the message. The message can display the artist, song title, call in phone numbers, etc. If the entire message can not be displayed, parts of the message appear every three seconds. To scroll through the message, press and release the INFO button. A new group of words displays after every press of this button. Once the complete message has displayed, the information symbol or INFO disappears from the display until another new message is received. The last message is displayed by pressing the INFO button. View the last message until a new message is received or you tune to a different station.

### MP3/CD Formatting Information for MP3/CD Radios

The MP3/CD equipped radios will play standard audio CDs, CD-Rs, and CD-RWs. The CD-R/RWs may contain either standard audio (*.cda) or compressed audio (*.mp3). Customers who record their own music CDs should be aware of the following:

• | The files can be recorded on a CD-R/RW disc with a maximum capacity of 700 MB.

• | The radio will play only compressed audio files recorded in the *.mp3 format. It also supports playlists that can be made and saved with popular MP3 software (in the *.m3u format). A playlist name must be no more than 32 characters in length. If the name of a playlist is longer than 32 characters, the radio will ignore the playlist.

• | The radio will only play audio from a CD-R/RW, it cannot record audio.

• | The radio will play a mixed mode CD-R/RW (one recorded with both *.cda and *.mp3 files). If a mixed mode CD is inserted in the radio, the radio will assign the standard CD audio to a directory which is listed as ROM audio directory.

• | ID3 tag information is displayed by the radio, if available. The ID3 tag information can either be version 1 or 2. The radio will display the filename, song name, artist name, album name, directory name, and playlist name, etc.

• | The radio supports multi-session discs, but only the files from the last session will be played.

• | There are a total of 20 directories (folders) allowed on a disc. The file structure can be 0-4 directories deep (a folder within a folder, within a folder, etc.) Anything more than 20 directories will be ignored. Each directory may have up to 99 files contained within it. Files not having the *.mp3 extension will not be played, but still count toward the maximum. Anything more than the first 99 files within a directory will be ignored. A single disc may have up to 254 files and directories. Anything beyond the 254 limit will be ignored.

• | MP3 files must be written to a CD-R/RW in one of the following industry-standard formats:

- | ISO 9660 Level 1

- | ISO 9660 Level 2

- | Joliet

- | Romeo

If the customer does not follow these guidelines when recording a CD-R/RW, the disc may not play in the MP3 Radio.

### Integral Multi Disc CD Changer (IMDX) (If equipped)

The integral multi disc CD changer has the capability of storing and playing up to six (6) compact discs. The integral multi disc CD changer has a shock-absorbing system. Only under extreme operating temperatures or severe shock or vibration should the compact disc player skip or mute. If the customer travels an abnormally rough road, a skip condition may be normal. Test drive the vehicle on a normal road with a known good CD. If the condition is still present, replace the radio. The use of CD lens cleaner discs is not advised, due to the risk of contaminating the lens of the CD optics with lubricants internal to the CD mechanism.

The CD mechanism within the ICDX radio will begin an initialization routine after a battery connect (e.g., connecting radio connector C1). The initialization process takes approximately 25 seconds to complete. It is very critical that the initialization is completed before removing battery power from the radio, in order for the complex moving parts of the CD mechanism to be positioned properly before shipping and/or handling purposes. Damage may result to the moving parts of the CD mechanism if battery power is removed during the initialization routine. The damage occurs to the CD mechanism during subsequent shipping or handling operations. The extent of the damage causes the CD mechanism not to recover and the mechanism becomes inoperative.

### Theft Deterrent

The radio theft deterrent system is intended to disable or limit radio functionality if an incorrect security code is programmed to the radio. The radio disables functionality if the security code programmed to the radio does not match the security code assigned to the vehicle. The radio compares the programmed security code to that received via serial data.

### OnStar®

When OnStar is activated, a serial data message is sent to the radio that activates a software program. When the software begins its process, the fade goes to the front, Bass and Treble are set to the mid range, the outputs are mono, and the audio source is OnStar. OnStar takes priority over any other audio source. All of these actions are preset values stored in the radio.

For additional OnStar information, refer to OnStar Description and Operation.

### Steering Wheel Controls

Some audio functions are available using the steering wheel controls. The steering wheel controls duplicate the function of the primary controls available on the radio.

For additional information on steering wheel controls, refer to Steering Wheel Controls Description and Operation.

### Speed-Dependant Volume Control (SDVC)

SDVC automatically adjusts the volume to compensate for road and wind noise as the vehicle increases or decreases speed while driving.