Radio/Audio System Description and Operation Part 1

RADIO/AUDIO SYSTEM DESCRIPTION AND OPERATION

Battery positive voltage is provided to the radio from the Radio (15A) fuse in the fuse block. The radio is grounded through a braided cable case ground. The radio is enabled/disabled by Class 2 messages from the body control module (BCM). The entertainment system on this vehicle is configured with a base and uplevel system. The base and uplevel systems contain a radio, antenna, speakers, and on some vehicles an audio amplifier.

The uplevel system differs from the base system by providing the customer with enhanced audio system features. Some of those features may include the radio data system (RDS), an audio amplifier, and programmable equalizer (EQ). Satellite digital radio (U2K) is available with the uplevel systems.

The following list shows the audio system RPOs available with this vehicle:
- Base Radio (U1C)- AM/FM Stereo, CD
- Uplevel Radio (UC6)- AM/FM Stereo, RDS, Multiple CD, EQ
- Uplevel Radio (US8) - AM/FM Stereo, RDS, EQ, CD, MP3
- Satellite Digital Radio (U2K)
- Speaker system custom- 6 (UW6)
- Speaker System premium- 7 (U65)- Includes subwoofer

Radio Features:

RADIO FEATURES

CD Features:

CD FEATURES

SONG LIST (UC6 ONLY)
The six-disc CD changer has a feature called song list. This feature is capable of saving 20 track selections.

To save tracks into the song list, perform the following steps:
1. Turn the radio on and load it with at least one CD.
2. Check to see that the CD changer is not in song list mode. S-LIST should not appear in the display. If song list mode is on, press the song list button to turn it off.
3. Select the desired CD by pressing the numbered push button and then use the SEEK left arrow to locate the track to be saved. The track will begin to play.
4. Press and hold the song list button for two or more seconds to save the track into memory. When the song list button is pressed, a beep with be heard immediately. After two seconds of pressing the button, two beeps will sound to confirm that the track has been saved and TRACK (number) ADDED will appear on the display.
5. Repeat Steps 3 and 4 for saving other selections.

SONG LIST FULL will appear on the display if your try to save more than 20 selections.

To play the song list, press the song list button. One beep will be heard and SONG LIST will appear on the display. The recorded tracks will begin to play in the order that they were saved.

Seek through the song list by using the SEEK arrows. Seeking past the last saved track will return you to the first saved track.

To delete tracks from the song list, perform the following steps:
1. Turn the CD player on.
2. Press the song list button to turn song list on. S-LIST will appear on the display.
3. Press either SEEK arrow to select the desired track to be deleted.
4. Press and hold the song list button for two seconds. After two seconds of continuously pressing the button, two beeps will be heard to confirm that the track has been deleted and TRACK (number) DELETED will appear on the display.

After a track has been deleted, the remaining tracks are moved up list. When another track is added to the song list, the track will be added to the end of the list.

To delete the entire song list, perform the following steps:
1. Turn the CD player on.
2. Press the song list button to turn song list mode on. S-LIST will appear on the display.
3. Press and hold the song list button for more than four seconds. A beep will be heard, followed by two beeps after two seconds, and a final beep with be heard after four seconds. SONG LIST EMPTY will appear on the display, indicating that the song list has been deleted.

If a CD is ejected, and the song list contains saved tracks from the CD, those tracks are automatically deleted from the song list. Any tracks saved to the song list again are added to the bottom of the list.

To end song list mode, press the song list button. One beep will be heard and S-LIST will disappear from the display.

MP3 Features:

MP3 FEATURE

Each item in the following list represents topics covered in detail below:
- AM/FM Reception
- XM Reception
- Antenna
- Audio Amplifier
- Theft Deterrent
- Radio Data System
- XM Satellite Radio
- XM Advisory Messages
- Radio Chime Level Adjustment
- Tape/CD Player Errors
- Technical Information for MP3 Player (US8)

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, or 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
- Which 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, or skip, off of the ionosphere

The AM frequencies have longer range due to the ground wave. The ground wave follows the curvature of the earth and is affected 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 mi).

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 mi). 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

XM Reception
XM satellite radio provides digital radio reception. The XM signal is broadcast from two satellites and, where necessary, terrestrial repeaters. The high power satellites allow the antenna to receive the XM signal even when foliage and other partial obstructions block the antennas view of the satellite. Terrestrial repeaters are used in dense urban areas. These repeaters will receive the satellite signal and re-broadcast them at much higher power levels in order to ensure reception in areas with densely packed tall buildings.

Antenna
The antenna is comprised of a fixed mast which is mounted on the body of the vehicle. Mast antennas are typically located on the fender or rear quarter panel of the vehicle.

Audio Amplifier
The purpose of the amplifier is to increase the power of a voltage or current signal. The output signal of an amplifier may consists of the same frequencies as the input signal or it may consist of only a portion of the frequencies of the input signal as in the case of a subwoofer or midrange amplifier.

When the radio is turned on, it sends a voltage signal to the audio amplifier via the radio on signal circuit. The gain control signal circuit allows the radio to recognize that the amplifier is present. Once the radio detects the amplifier, the radio will output low-level signals to the amplifier. With the amplifier enabled, the signal that drives the speaker is now amplified.

Theft Deterrent
The "Theftlock" theft deterrent system is a feature on all base and uplevel radios. There is no need to program a security code into the radio as in past model years. The theft deterrent system now utilizes class 2 serial data to determine if the radio is in the appropriate vehicle. Each time the radio receives the "run" power mode message, it compares the VIN information it has stored to the VIN information received from a module on the class 2 serial data circuit responsible for transmitting that information. If a mis-match occurs, the radio display will indicate to the user the radio is locked. Once this takes place, a DTC will set, the radio will not respond to any button presses and become inoperative. The two scenarios able to cause this condition are:
- A radio is installed from another vehicle.
- A module which communicates on the class 2 serial data circuit which supplies VIN information to the radio is replaced and not properly setup with the correct VIN information for that vehicle.

The only way to unlock the radio is by using a scan tool. Always refer to the table to diagnose the "Theftlock" DTC for further information.

Radio Data System (RDS)
All uplevel audio systems are equipped with technology known as the Radio Data System (RDS). RDS is a system that sends data along with the audio of the FM station you are currently tuned to. RDS is a standard that defines how a FM broadcast station may send digital data along with the audio program. Think of it as a one way wireless modem, allowing the broadcaster to send information about the program to your receiver.

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 or other audio programs that are not audible in the main audio program. RDS information can be used to display program information and to control the radio.

To receive the RDS signal, all that is needed is an FM receiver with an RDS circuit. A special integrated circuit capable of dealing with the RDS signal is in the RDS circuit and passes it along to the receiver's microprocessor where it is decoded and acted upon.

RDS Basic Information
- RDS functions are provided in the FM broadcast band only.
- 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.
- 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.

Displaying RDS Information
The RDS feature is always on. When tuned to a non-RDS station, the radio will display frequency information as you would normally expect. When tuned to an RDS station, the radio can operate as follows:
- The radio will change from displaying the frequency of the FM station to displaying the call letters of the station or display the nickname of the station.
- Display the type of program.
- Display general information such as artist and song title, call in phone numbers, etc.

Viewing and Selecting RDS Information for Display
Press the TUNE knob once for less than 2 seconds when the radio displays the program service (PS) name and the frequency of the station will be displayed. Press the knob again, and the program type (P-Type) will be displayed. Pressed again, and the program type (PTY) name will be displayed, if the broadcaster is broadcasting one. The PTY name is an eight-character name that the broadcaster may use to further identify the type of programming currently being broadcast. Should you decide that Frequency, P-Type or PTY name is more desirable to display when tuned to an RDS station than the PS name, press the TUNE knob until the desired information is displayed, then press and hold for more than 2 seconds. A beep should be heard and the radio will now display the selected information whenever tuned to an RDS broadcaster. The radio will display frequency for all non-RDS broadcast stations.

Using RDS Program Types to Tune Radio
Listed are several ways on how to tune your radio using RDS program types.

The radio will now be configured to tune based on RDS data rather than frequency.

A Fast Way to Find a RDS Station In Your Listening Area
1. Press the PROG TYPE or P-TYPE button, the radio displays the current P-Type to search for.
2. Rotate the TUNE SELECT RCL knob until the radio displays "ANY TYPE". Press the SEEK SCAN button again and the radio will now seek the first RDS Broadcaster of any kind that it can find in the FM band.

Finding a RDS Station By Specific Program Type
1. Press the PROG TYPE or P-TYPE button, the radio will display the current P-Type to search for.
2. Rotate the TUNE SELECT RCL knob until the desired program type is shown in the display.
3. Press the SEEK SCAN button and the radio will now seek the first RDS Broadcaster of the selected P-Type.

If the radio cannot find the desired P-Type, the radio displays "NOT FOUND" and will return to the last station you were listening to.

Using the INFO Feature
When the INFO icon appears in the radio display, a new text message is available for viewing. These text messages are from the RDS broadcaster to the listening public and may be general information such as artist and song title, call in phone numbers, etc.

How to View the INFO Message
- To view the message when the INFO icon appears, press the INFO button to display the text message. If you do not press the INFO button again, the text message will automatically be displayed 8 characters at a time, 3 seconds between updates.
- To view the text message faster, press the INFO button for less than 1 second to scroll through the message at your own speed.
- The INFO icon disappears as soon as you press the INFO button. The INFO icon will appear when a new different message is received.
- To view the most recent received message, press the INFO icon at any time, even if the icon does not appear in the display.