Radio/Audio System

RADIO/AUDIO SYSTEM DESCRIPTION AND OPERATION

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 (UM7) - AM/FM with Cassette
- Radio (UB0) - AM/FM with CD
- Radio (UB1) - AM/FM, Cassette and CD
- Radio (UC6) - AM/FM, Integral Multi Disc CD Changer
- Navigation Radio (UM8) - RADIO - AM/FM Stereo, Seek/Scan, CD, ETR, Navigation, Clock

Radio Features:

RADIO FEATURES

Navigation Display Head, UM8:

UM8 NAVIGATION RADIO FEATURES

Cassette Features:

CASSETTE FEATURES

Compact Dist Features:

COMPACT DISC FEATURES

Each item in the list below represents topics covered in detail below.
- AM/FM Reception
- Diversity Antenna System
- Audio Amplifier
- Theft Deterrent
- Integral Multi Disc CD Changer (IMDX)
- Remote Playback Device
- Radio Data System (RDS)
- Tape/CD Player Error Messages
- Rear Seat Audio (RSA)
- XM Satellite Radio

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 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

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.

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
- The radio antenna module is not grounded properly. The module grounding screws should be clean and tight. The antenna module ground is either a chassis ground or a ground strap. Measure the resistance from the antenna module base plate to a good ground. Resistance should be 0.20 ohms or less. Find and correct the condition if the resistance is out of specification.
- The antenna enable signal is not present at the radio antenna module. This could be caused by an output failure of the radio or an open/shorted antenna enable signal circuit. In order to test the antenna enable signal circuit, the radio must be ON and tuned to the FM band. Disconnect the radio antenna module. Measure the voltage from the antenna enable signal circuit of the radio antenna module to a good ground. Voltage measured should be near 12 volts. If the specified voltage is measured, test the antenna enable signal circuit for an open or short to ground. If no failures were found, replace the radio.
- The FM composite signal circuit to the radio antenna module is open or shorted to ground. Test the FM composite signal circuit for an open or short to ground.
- The feed coax at the radio antenna module has been inadvertently swapped with the FM impedance matching module crossover coax. Ensure that the feed coax, marked with a yellow band, is in the correct socket on the radio antenna.
- Improper retention of the antenna cable in the floating retainer. Poor or no connection with the radio will result when the radio is installed if the antenna cable is not properly attached in the floating retainer. Inspect the antenna cable for movement in the floating retainer. Replace the antenna cable if movement is found.
- Defective radio antenna module-Replace radio antenna module.

Poor Reception on AM Band Only
- Defective AM antenna
- Defective radio antenna module-Replace radio antenna module.

Poor Reception on FM Band Only
- Defective primary or secondary FM antenna
- Defective radio antenna module-Replace radio antenna module.
- Defective FM impedance matching module-Replace FM impedance matching module.

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 2 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.

The digital radio receiver utilizes class 2 serial data to determine if it is in the appropriate vehicle. Each time the digital radio receiver receives the run power mode message, it compares the VIN information received from the body control module (BCM) on the class 2 serial data circuit. If a mis-match occurs, the radio display will indicate to the user the digital radio receiver is locked. The digital radio receiver cannot be unlocked, it must be replaced. The 2 scenarios able to cause this condition are:
- A digital radio receiver is installed from another vehicle
- The BCM is replaced and not properly setup with the correct VIN information for that vehicle

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 re-intiated if desired by depressing the load button again for more than 2 seconds. If the changer is full, six 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 one and a half 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. 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
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.

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:
- The name of the station
- The type of program
- General information such as artist and song title, call in phone numbers, etc.

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:
- Interrupt the playback of your cassette or CD for traffic or emergency bulletins
- Search for stations by type of program
- Automatically follow network programming from transmitter to transmitter as you travel from one listening area to another
- Set your clock to the time that the RDS Broadcast station broadcasts

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 broadcasters 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:
- Press and hold the AM/FM button for 2 seconds or more.
- The radio will display AF ON or AF OFF depending on the current condition of AF and a confirmation beep will be heard.

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 AFs 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 broadcast once a minute. To set the clock using RDS clock data perform the following:
- Press and hold the HR and MIN buttons together for two or more seconds to update the time.
- The display will show UPDATED after receiving the broadcast time data.
- If the broadcaster is not broadcasting the time data, the radio will display NO UPDATE and the time remains unchanged.

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 audio portion of the rear seat audio 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 shall have 2 stereo volume controls to vary the audio volume to the headphones. For each headphone, one 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.

XM Satellite Radio

XM Advisory Messages:

XM satellite radio provides digital radio reception. The XM signal is broadcast from 2 satellites and , where necessary, terrestrial repeaters. The high power satellite 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 rebroadcast them at much higher power levels in order to ensure reception in areas with densely packed tall buildings. Xm is a national satellite radio service that offers up to 100 coast-to-coast channels including music, news, sports, talk, and children programming. XM provides digital quality audio and text information, including song title and artist name. A service fee is required in order to receive the XM service. For more information contact XM at www.xmradio.com or call 1-800-852-9696

Digital Radio Receiver
The radio communicates with the digital radio receiver via the class 2 communications circuit. The digital radio receiver sends low level audio signals to the audio amplifier.

Steering Wheel Controls
Some audio functions are available using the steering wheel controls. The steering wheel controls consist of multiple momentary contact switches that connect a series of resistors. When a steering wheel control button is pressed, a specific resistance value is noted by the BCM. This results in a generated voltage, unique to the particular button. The BCM alerts the radio that the button has been pressed, and the radio responds, just as if the corresponding radio front panel button had been pressed.

Amplifier
The amplifier in early build vehicles is a class 2 device that communicates with the scan tool on the Class 2 bus. The Class 2 amplifier will set a U100 in the radio if there is a communication problem. The late build vehicles have a NON-Class 2 amplifier that does not communicate over the Class 2 bus and therefore the NON-Class 2 amplifier will not set codes. Both amplifiers have similar operating characteristics, therefore, there are not separate diagnostics for the NON-Class 2 amplifier.