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

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.

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.

Tune

Turn the TUNE/RCL/P-TYPE 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

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/RCL/P-TYPE 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 w/AUDIO knob.

Bass, Treble or Midrange

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

Programmable Equalizer

Press the AUDIO EQ 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 FWD button.

Reverse

Press the REV button.

Auto Reverse

Yes

Previous

Press the down arrow on SEEK/SCAN button.

Next

Press the up arrow on SEEK/SCAN button.

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 FWD button.

Press the arrow on FWD button.

Reverse

Press the REV button.

Press the arrow on REV button.

Seek

Press the up or down arrow on SEEK/SCAN button.

Press the left or right arrow on SEEK/SCAN button.

Scan

Press the up or down arrow on SEEK/SCAN button.

Press the left or right arrow on SEEK/SCAN button.

Repeat

N/A

Press the RPT button.

Random

Press the RDM button.

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

    • AM/FM Reception
    • Antenna
    • Audio Amplifier
    • Theft Deterrent
    • Radio Data System (RDS)
    • 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 (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

Antenna

The antenna is comprised of a very thin metal grid which is permanently affixed to the top center of the windshield. If the antenna becomes damaged, the windshield must be replaced.

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 audio amplifier on this vehicle is turned on when it receives the antenna enable signal from the radio.

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 his 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 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 two 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 and performs 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.

Viewing and Selecting RDS Program Type Information

The Program Type feature is activated by pressing the program type button, labeled PROG TYPE or P-TYPE. The program type name will be displayed if the broadcaster is broadcasting one. The program type name is an eight-character name that the broadcaster may use to further identify the type of programming currently being broadcast. Turn the SELECT or P-TYPE knob to select the desired program type. If a station with the selected program type is not found, the radio displays "NOT FOUND".

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 for two 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 for two 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.

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:

    • Press and hold the AM-FM button for two seconds or more.
    • The radio will display "AF ON" or "AF OFF".

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:

    • 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.

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.
       - Tight tape.
       - Broken 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 the time, if the unit is off, or display the radio frequency for 5 seconds, then the default, if the unit is on.
       - Check CD-Optics focus error, maybe due to moisture.
       - Check CD-Optics loss of tracking control, maybe due to blemishes on disc.