GM Service Manual Online
For 1990-2009 cars only
Table 1: Radio Features
Table 2: Cassette Features
Table 3: Compact Disc Features
Table 4: XM Advisory Messages

The radio receives power from the RADIO fuse in the junction block-right I/P. Ground is provided via G201 and G202. The radio is enabled/disabled by class 2 messages from the body control module (BCM). The radio routes audio signals from the digital radio receiver or the vehicle communication interface module (VCIM) to the speakers and/or amplifier when directed by class 2 messages.

The Entertainment System on this vehicle is configured with an AM/FM stereo radio with the radio data system (RDS) and either a cassette player or a CD player or both. CD and cassette. The uplevel system provides the customer with extended range speakers and an audio amplifier. Satellite digital radio (U2K) is available with uplevel systems.

The following list shows the radios available for this vehicle:

    • Radio (ULO) - AM/FM Stereo, Cassette with RDS
    • Radio (UNO) - AM/FM Stereo, CD and RDS
    • Radio (UPO) - AM/FM Stereo, Cassette with CD and RDS

Radio Features

Controls

All Radios

Power

Push the PWR/VOL knob to turn the radio on.

Volume

The volume is adjusted by rotating the PWR/VOL knob.

Speed Compensated Volume (SCV)

Press the AUTO VOL button. The available settings are OFF, LOW, MEDIUM, and HIGH.

Tune

Turn the TUNE/DISP knob.

Seek

Momentarily press the SEEK/SCAN button.

Scan

Hold the SEEK/SCAN button at least 2 seconds.

Presets

Six AM, Six FM1 and Six FM2. Six XM1 and Six XM2 if equipped with U2K.

Preset Saving

Press and hold desired button until an audible beep is heard.

Preset Seek

Steering Wheel Control only

Preset Scan

Hold the SEEK/SCAN button at least 4 seconds.

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/DISP knob.

Mute

Steering Wheel Control only

Fade or Balance

Push and release the AUDIO knob until fade or balance appears in the display and adjust by rotating the AUDIO knob.

Bass, Treble or Midrange

Push and release the AUDIO knob until bass, mid, or treb appears in the display and adjust by rotating the AUDIO knob.

Programmable Equalizer

Press the AUTO TONE button to cycle through the preset equalization settings.

Cassette Features

Controls

ULO

UPO

Play/Stop

Press the TAPE/AUX button.

Press the CD/TAPE button.

Eject

Press the EJECT button.

Forward

Press the preset button 4.

Reverse

Press the preset button 3.

Auto Reverse

Yes

Previous

Press the left arrow on SEEK/SCAN button, or press the preset button 1.

Next

Press the right arrow on SEEK/SCAN button, or press the preset button 2.

Side

Press the preset button 5.

Compact Disc Features

Controls

UNO

UPO

Play/Stop

Press the CD/AUX button.

Press the CD/TAPE button.

Eject

Press the EJECT button.

Forward

Press the preset button 4.

Reverse

Press the preset button 3.

Previous

Press the left arrow on SEEK/SCAN button, or press the preset button 1.

Next

Press the right arrow on SEEK/SCAN button, or press the preset button 2.

Repeat

N/A

Press the RPT button.

Random

Press the RDM button, or preset button 6.

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

    • AM/FM Reception
    • XM Reception
    • Antenna
    • Audio Amplifier
    • Theft Deterrent
    • Radio Data System (RDS)
    • XM Satellite Radio
    • XM Advisory Messages
    • Radio Chime Level Adjustment
    • Steering Wheel Controls
    • Tape/CD Player Error Messages

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 an active rear window antenna system. The radio sends the antenna enable signal to the radio antenna module which enables coupling of the RF signal from the rear window antenna grid to the radio.

Audio Amplifier

The purpose of an audio amplifier is to increase the power of a voltage or current signal. The output signal of an amplifier may consist 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 a mid-range amplifier.

Power is supplied to the audio amplifier via the RADIO fuse in the Junction Block-Right I/P. Ground is provided to the amplifier by G202. When the radio is turned on, the radio sends a voltage signal to the audio amplifier via the antenna enable circuit. This circuit enables the audio amplifier to amplify the speaker output circuits from the radio. The audio amplifier sends the speaker output signals to drive the appropriate speakers.

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 in this section 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.

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 networked 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.

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 TRAF 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 on 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".

Traffic Interrupt Feature

Whenever the TRAF icon is displayed, the current FM station may also broadcast traffic announcements. Traffic announcements are reports of the current traffic conditions in the listening area of the tuned FM broadcasters.

Your radio can interrupt the playback of a cassette or compact disc by use of the traffic interrupt feature. The traffic interrupt feature is enabled when the TRAF icon is displayed.

If the broadcaster sends out a traffic announcement while you are listening to FM or in the playback mode, "TRAFFIC" will be displayed on the radio and the audio from the broadcaster will be heard. At the conclusion of the traffic announcement, the radio will return to the previous playback mode.

During the time the radio displays "TRAFFIC", you can adjust the volume of the traffic announcement. This will be the volume at which all future traffic announcements will be heard until the volume during another traffic announcement.

You can also interrupt a traffic announcement interrupt by pressing the TRAF button.

RDS Program Type Interrupts

When the Program Type feature is on, all program types may be selected as interrupts. Perform the following to select a program type as an interrupt.

  1. Turn ON the radio.
  2. Select the program type.
  3. Press and hold the program type button, labeled PROG TYPE or P-TYPE, for 2 seconds while the program type is displayed.

When an interrupt is set, the display shows the program type followed by an asterisk and the brackets around the [P-TYPE] icon are illuminated.

To turn an interrupt off:

  1. Select a program type marked as an interrupt.
  2. Press and hold the program type button, labeled PROG TYPE or P-TYPE, for 2 seconds. The program type will be unmarked by turning off the asterisk. If no other program type interrupts are set, the brackets around the [P-TYPE] icon are also turned off.

When a Program Type Interrupt is set, the radio will wait for the current FM RDS station to change its program type to one of those selected as an interrupt. When the station program type changes to a program type interrupt setting then the interrupt is activated. If the radio is in a playback mode, an interrupt will cause the radio to switch to the FM band, display the program type followed by "INT", and adjust the volume to the last active interrupt volume. If the radio is in the FM mode when an interrupt occurs, only the volume will change. The radio resumes the mode that was active prior to the interrupt, when an interrupt ends. An interrupt in progress may be canceled by pressing the program type button or a mode button.

During a national or local emergency, a special program type interrupt message "ALERT!" is displayed. This special announcement will cancel all other RDS features that are in progress, such as a traffic announcement.

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:

    • Press and hold the AM/FM or BAND button for two 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 an 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:

    • 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 broadcasted time data.
    • If the broadcaster is not broadcasting the time data, the radio will display "NO UPDATE" and the time remains unchanged.

XM Satellite Radio

XM is a national satellite radio service that offers up to 100 coast to coast channels including music, news, sports, talk and children's 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 controls communicate with the digital radio receiver via the class 2 communication circuit. The digital radio receiver sends remote radio audio signals to the radio.

Viewing Messages

Press the DISP or RCL button while in XM mode to view various pieces of information related to the current song or channel. By pressing and releasing the DISP or RCL button, you may view four different categories of information: Artist Name/Feature, Song/Program Title, Channel Category, and other Additional Information that may be broadcast on that channel. Additional Information messages may not always be available. If an Additional Information message is being broadcast on the tuned channel, the INFO icon will appear on the display. Each of the four information types may have multiple pages of text. To reach a category, press and release the DISP or RCL button consecutively until the desired type is displayed. If there are multiple pages of text for the selected information type, the radio will automatically display all the pages for that type at a rate of approximately one page every three seconds before timing out and returning to the default display. You may override this feature by pressing the DISP or RCL button to review all of the pages at your own pace.

XM Advisory Messages

Radio Display Message

Condition

Updating

Updating encryption code

No Signal

Loss of signal

Loading XM

Acquiring channel audio (after 4 second delay)

CH Off Air

Channel not in service

CH Unavail

Channel no longer available

No Info

Artist Name/Feature not available

No Info

Song/Program Title not available

No Info

Category name not available

Not Found

No channel available for the chosen category

No Info

No text/informational message available

XM Locked

Theft Lock active

Radio ID

Electronic serial number (ESN) channel 0

Unknown

Radio ID not known (should only be if hardware failure

Chk XMRcvr

Hardware failure

Radio Chime Level Adjustment

Important: Radio chime level adjustment is only available on radios equipped with RDS.

The radio is the vehicle chime producer. The chime is audible from the driver's side front door speakers.

To adjust the chime level louder.

  1. Turn ON the ignition.
  2. Turn OFF the radio.
  3. Press and hold preset button 6.

The chime volume level will change from the normal level to loud. The radio displays "LOUD".

To change back to the default or normal setting follow the previous steps. The chime volume level will change from the loud level to normal. The radio displays "NORMAL".

Each time the chime volume is changed, the radio sounds three chimes as an example of the new volume selected.

Steering Wheel Controls

Some audio functions are available using the steering wheel controls. The steering wheel controls are actually a resistor network that consists of multiple momentary contact switches and a series of resistors. The switches and resistor network are arranged so that each switch has a different resistance value. When a switch is pressed, a voltage drop occurs in the resistor network, which produces a specific voltage value unique to the switch selected. These specific voltage values allow the radio to identify which switch has been pressed.

The radio supplies voltage to the steering wheel control switch via the radio on signal circuit. The specific voltage signal from the switch is returned to the radio on the steering wheel controls signal circuit.

Tape/CD Player Error Messages

The radio displays an error when any of the following occurs.

    • The radio will display error codes for the tape player and integral CD player.
    • The radio will display the following tape player error codes for tight tape, broken tape, and wrapped tape. If these conditions are detected, the radio will switch to the radio mode and eject the tape. The error code will be displayed for 5 seconds, followed by the tuner display, then the default.
       - E10 or TIGHT TAPE-Tight tape
       - E11 or BROKEN TAPE-Broken tape
       - E14 or WRAPPED TAPE-Wrapped tape
    • The radio will display the following integral CD player error codes. If one of these problems is detected, the unit will switch to the radio mode and eject the CD. The display will show TOD, if the unit is off, or display the radio frequency for 5 seconds, then the default, if the unit is on.
       - E20 or CHECK CD-Optics focus error, maybe due to moisture
       - E21 or CHECK CD-Optics loss of tracking control, maybe due to blemishes on disc
       - E22 or PLAYER ERR-Load/Unload motor problem
       - E23 or PLAYER ERR-Communication problem