Table 1:	Radio Features
Table 2:	Cassette Features
Table 3:	Compact Disc Features

The entertainment system on this vehicle is configured with a radio, antenna, and speakers.

The following list shows the radios available for this vehicle:

Radio Features

Controls	All Radios
Power	Push the PWR/PUSH/VOL knob to turn the radio on.
Volume	The volume is adjusted by rotating the PWR/PUSH/VOL knob.
Automatic Volume Control	Press the AUTOVOL button.
Tune	Turn the TUNE/SELECT/PUSH RCL knob.
Seek	Momentarily press the SEEK/SCAN button.
Scan	Hold the SEEK/SCAN button at least 4 seconds.
Presets	6 AM, 6 FM1 and 6 FM2
Preset Saving	Press and hold the desired button until an audible beep is heard.
Set Clock	Press and hold the HR or MN button until an audible beep indicates the time set mode has been entered. Once the beep is heard, the time can be set by tapping each button to incrementally adjust the time. Holding down each button will rapidly change the time.
Recall	Push the TUNE/SELECT/PUSH RCL knob.
Fade or Balance	Press the BAL/FADE button to select and adjust w/SELECT knob.
Bass, Treble or Midrange	Press the TONE button to select and adjust w/SELECT knob.
Automatic Tone	Press the AUTO TONE button.

Cassette Features

Controls	UP0 Radio
Eject	EJECT button
Fast Forward	Preset button 1
Reverse	Preset button 4
Auto Reverse	Yes
Side	Preset button 5
Previous	Preset button 1
Next	Preset button 2
Dolby	Preset button 6
Repeat	NA

Compact Disc Features

Controls	UN0 Radio	UP0 Radio	UC6 Radio
Eject	EJECT button
Fast Forward	Preset button 1
Reverse	Preset button 4
Disc	Preset button 5
Previous	Preset button 1
Next	Preset button 2
Dolby	Preset button 6
Repeat	NA
Random	Preset button 6

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

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:

AM Reception

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

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 mi).

FM Reception

The shorter wavelengths of the higher frequency FM band:

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:

Diversity Antenna System

Important: This diversity antenna system is comprised of 3 glass mounted antennas, a radio antenna module, and an FM impedance matching module. The primary AM and FM antennas are an integral part of the left rear quarter glass and are connected to the radio antenna module. The secondary FM antenna is an integral part of the right rear quarter glass and is connected to the FM impedance matching module. The radio antenna module processes the antenna reception signals and phase aligns them to create one strong signal. The FM impedance matching module boosts the secondary antenna signal and transmits it to the radio antenna module.

The following information lists the most probable cause of the concern to the least probable cause followed by the appropriate test for that condition. If the test leads to the replacement of a component, always inspect for a poor connection before proceeding with the replacement. If the test leads to the replacement of a component, always inspect for a poor connection before proceeding with the replacement. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Perform the Antenna System Test and test the antenna coax cable prior to performing any of the following tests.

Poor Reception on Both AM and FM Bands

Poor Reception on AM Band Only

Poor Reception on FM Band Only

Audio Amplifier

The audio amplifier is standard on some vehicle lines but is optional on most. The radio supplies low level audio signals to the audio amplifier in order to boost the signal sent to the speakers. The class 2 signal circuit allows the radio to recognize that an amplifier is present. Once the radio detects an audio amplifier, it will output low level audio signals. The audio amplifier is turned on when it receives a message via the class 2 serial data circuit indicating that the radio is on.

Theft Deterrent

The 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:

1. A radio is installed from another vehicle.
2. 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 in this section to diagnose the "Theftlock" DTC for further information.

Integral Multi Disc CD Changer (IMDX)

The Integral Multi Disc CD Changer has the capability of storing and playing up to 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.

To operate the Integral Multi Disc CD Changer in the single play mode, depress the "LOAD" button for less than 2 seconds, an audible "beep" can then be heard. When the disc door opens the LED to the right of the disc door will first turn red then green to indicate the CD can be loaded. The radio will also display the message "INSERT CD 1" and the changer will pull the disc into the play position. To operate the changer in the multi disc mode, depress the "MODE" button for more than 2 seconds and the LED to the right of the disc door will first turn red then green to indicate CDs can be loaded. The radio will also display the message "MULTI LOAD" to indicate the multi load mode has been initiated and the changer will begin accepting a disc for however many empty slots there may be. If 8 seconds elapse before the next disc is loaded, the multi load mode is cancelled and can be reinitiated if desired by depressing the load button again for more than 2 seconds. If the changer is full, (6 discs are loaded) the single play and multi load modes cannot be executed. When this occurs, 3 audible beeps are heard and the message "CHANGER FULL" is displayed.

Remote Playback Device

The remote playback device is either installed at the factory or in some instances it is dealer installed. There are 3 types of remote playback devices, a multi disc remote CD changer, a single disc CD player and a cassette player. All 3 devices have a wiring harness which plugs into the back of the radio. The radio controls and communicates with the remote playback device through a Entertainment and Comfort (E&C) or Class 2 communication circuit.

Remote CD Changer (CDX)

The remote CD changer allows for multiple compact disks to be played continuously without having to manually change compact discs. Normal size discs may be played using the slots supplied in the magazine. The magazine must first be loaded with discs before it can played. To load CDs, insert the CDs from bottom to top, placing the discs in the magazine label side up. If a disc is loaded label side down, the disc will not play and an error will occur. Care should be used to align and insert the disc into one disc tray only. Repeat this procedure for loading all of the discs in the magazine. Once the discs are loaded into the magazine, push the magazine into the changer in the direction of the arrow marked on the magazine. When the CD magazine is loaded, the changer will begin checking for discs in the magazine. This will continue for up to 1 1/2 minutes, depending on the number of discs loaded. To eject the magazine from the player, push the CD changer door. The door will open. Then press the eject button.

Important:  If the CD magazine fails to eject after the EJECT button has been pressed, do not attempt to pry the magazine from the CD changer. Whenever a CD magazine with discs is loaded in the changer, the CD changer symbol will appear on the radio display. If the CD changer is checking the magazine for CDs, the CD symbol will flash on the display until the changer is ready to play.

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 his program to your receiver.

RDS data is carried in what is known as a "sub-carrier". A sub-carrier 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 a 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

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

Broadcast RDS information can be used in a variety of ways by the receiver and listener, but basically falls into 2 categories: Display and Control.

Displaying Program Information

RDS displays textual information such as:

RDS is always on. When tuned to a non-RDS station, your radio will display frequency information as you would normally expect. When tuned to a RDS station, your 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. This feature is known as the Program Service Name.

Controlling the Radio

RDS can control the radio when data the receiver can use responds to timely information performing the following:

Viewing and Selecting RDS Information for Display

Press the "TUNE SELECT PUSH RCL" knob once for less then 2 seconds when the radio displays the program service 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 name will be displayed (if the broadcaster is broadcasting one). The program type name is an 8-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 program type name is more desirable to display when tuned to an RDS station than the Program Service Name, press the "TUNE SELECT PUSH RCL" 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 the RDS Traffic Feature

Some RDS broadcasters may carry traffic information programming to inform you of current traffic conditions in your listening area and is indicated by the icon in the radio display. RDS enables the broadcaster to get this information to you even when you are listening to a tape or compact disc. This feature can be enabled or disabled by the listener. Press the "TRAF" button to find a station that claims to carry traffic information. You may do this even when playing a cassette tape or compact disc. This action will operate in the background without interrupting the current playback. If the radio is not currently tuned to an RDS traffic station, the radio will immediately SEEK an RDS traffic station. If the radio finds an RDS traffic station, the" TRAF" icon will appear in the radio display as will brackets around the (TRAF) icon. If the radio cannot find an RDS traffic station after searching through the entire FM band, the radio will display "NO TRAFFIC".

Alternate Frequency (AF) Switching

RDS permits broadcaster's to send information to the radio that allows the radio to automatically switch frequency to the best quality station in that broadcaster's network.

Since the radio is displaying the broadcaster call letters or nickname, the listener will not see the frequency during an AF switch unless you have changed the default display to be frequency instead of Program Service name.

To enable or disable AF switching perform the following:

When AF is enabled and you recall a RDS station stored on preset, the radio determines if the station stored is of acceptable quality. If not, the radio checks all available AF's for your station. If the radio fails to locate your program, AF SEARCH will be displayed as the radio scans across the band looking for your program or an affiliated network. If the radio cannot find the original station or an acceptable alternate frequency NOT FOUND will be displayed and the radio returns to the original frequency for the preset.

RDS Clock Time

Broadcasters can choose to send clock time information in the RDS data. This information can be used to update the clock time on the radio. RDS clock time is broadcasted once a minute. To set the clock using RDS clock data perform the following:

Radio Error Messages

The radio displays the following error messages:

CDX ERR: Displays if communication is lost with the remote CD changer (if equipped).

CHECK CD: Displays when the player encounters a focus or tracking error.

CHK CDXX: Displays when the CD changer encounters a focus or tracking error (if equipped).

CHK TAPE: Displays if a tape has been inserted but is unable to be played due to an error.

DOOR OPEN: Displays when the CD changer door has been left open (if equipped).

NO DISC: Displays when the radio expected a disc to be inserted.

NONE: Displays when the radio is unable to detect the vehicle speed data information via the class 2 serial data circuit.

Voice Recorder

To record a message, press the button with the circle on it and begin speaking. Press the button with the circle on it again to stop recording. System allows you to record up to 4 minutes of messaging.

You may also press and hold the button with the circle on it while you are speaking and then let it go when you are finished.

To play back messages, press the button with the right arrow on it. Pressing the right arrow button more than once will return you to previously recorded messages. If you press and hold this button for more than one second, all of the recorded messages will be played back.

To delete messages, press the button with the square on it while the message is playing. If you press and hold the right arrow button and the circle button at the same time for a half of a second, all of the messages will be deleted.

Rear Seat Audio (RSA)

The Rear Seat Audio and Rear HVAC control functions in the GMT 360/370/800 programs are combined into 1 dual function control unit. The audio portion of the controller provides dual audio source capability from the vehicle audio system.

When in use, the audio portion of the controller enables rear seat occupants to listen to a different music source than the front seat occupants. The audio volume at each headphone is independently controlled by the rear passengers. A VF display in the center of the controller provides graphic communication to the rear seat operator the state of various rear audio functions. The dual source mode functionality is an embedded feature of the compatible radio receiver. Primary radio controls always have control of the front speaker outputs. Primary radio mode control is not affected by the operation of the rear audio control and always has priority over the rear audio control.

The front seat occupants have the capability to override and disable the rear audio controller operation through the primary radio controls. An ignition cycle also causes the rear audio to default to the "off" state.

Even when the primary radio is powered "off", shutting off all speakers in the vehicle, the RSA controller functions are available. The rear passengers can still listen to any available audio source through the headphones.

The controller has 2 stereo volume controls to vary the audio volume to the headphones. For each headphone, 1 element will provide the variable load to the "left" audio output and the other element will provide the variable load to the "right" audio output.