Contents
| • | Regular production option (RPO) |
| • | Features |
| • | Circuit description |
| • | Component description |
| • | Customer tips |
| • | On-board diagnostics (OBD) |
| • | Theft deterrent feature |
RPO Options
The entertainment system on this vehicle is configured with either a base or uplevel audio system. Both the base and uplevel audio systems contain a radio, antenna, and speakers.
The following shows the entertainment regular production options (RPOs) that are available for this vehicle:
| • | (UM7) AM/FM Stereo |
| • | (U1C) AM/FM Stereo CD |
| • | (US8) AM/FM Stereo, CD, MP3, RDS, EQ |
| • | (US9) AM/FM Stereo, 6-Disc CD, MP3, RDS, EQ |
| • | (UXQ4) Base Four Speaker |
| • | (U79) Uplevel Four Speaker |
| • | (WBM) Premium Audio |
| • | (U2K) Digital Radio |
Circuit Operation
Radio Power: The main radio power is supplied by the 10A RADIO (BATT1) fuse in the body control module (BCM). Radio switch-on power, 12 volts in ACC or RUN, is supplied by the 10A RADIO (ACC) in the BCM.Radio Grounds: The main radio ground provides a ground for the radio circuits. An additional braided ground strap provides a shielding radio case ground to reduce electromagnetic interference (EMI) noise. Both grounds are connected together inside the radio.
Radio Speaker Outputs: At zero volume, the plus (+) and minus (-) speaker outputs are both approximately 5-6 volts, measured to vehicle ground. If a plus or minus for any speaker output is shorted to ground or voltage, the radio circuitry will turn OFF all 4 speaker outputs for component protection. Above zero volume, the plus and minus change to create a voltage difference between each other, to drive the voice coil of the speaker.
Radio Park Lamp Input: The radio park lamp input allows the radio to sense when the vehicle parking lamps are ON. When the parking lamps are ON, this circuit goes to battery voltage, and the radio display back-lighting switches from full bright to the brightness level determined by the instrument panel (I/P) illumination input.
Radio I/P Illumination Input: A pulse width modulated (PWM) voltage for I/P illumination is provided to the radio I/P illumination input. The radio uses this input to directly illuminate the radio buttons and adjust the radio display back-lighting when the park lamp input is ON.
Amplifier Power: The main amplifier power is provided by the 20A PREM AUDIO fuse in the I/P fuse block.
Amplifier Radio Speaker Inputs (WBM only): The radio speaker outputs, at a reduced output level for amplified systems, are the amplifier inputs. The amplifier boosts these inputs and outputs them to the vehicle speakers. Speaker plus and minus circuits from the radio change to create a voltage difference between each other. If one speaker plus or minus is open between the radio and the amplifier, the input to the amplifier is approximately half because only one of the circuits is changing. The speaker for that channel then operates at approximately only half the normal volume.
Amplifier Speaker Outputs (WBM only): At zero volume, the plus (+) and minus (-) speaker outputs are both approximately 5-6 volts, measured to vehicle ground. If a plus or minus for any speaker output is shorted to ground or voltage, the amplifier circuitry will turn OFF either the front outputs or rear outputs for component protection. Above zero volume, the plus and minus change to create a voltage difference between each other, to drive the voice coil of the speaker.
Amplifier Radio-On (WBM only): When the radio is ON, this circuit is pulled to 12 volts by the radio. The amplifier switches ON when this circuit is 12 volts and switches OFF when this signal is 0 volts.
Remote Radio Audio Signal Inputs (UE1 only): Audio output from the OnStar® communications module connects to the remote audio signal inputs of the radio. When the cellular telephone mute signal goes to 0 volts, the radio over-rides any other audio signal and uses these inputs as the source for output to the speakers.
Cellular Telephone Mute (UE1 only): The OnStar® communications module uses the cellular telephone mute signal circuit to over-ride the radio for OnStar® communication. When cellular telephone mute is not active, this circuit is held at 2 volts by the radio. When the cellular telephone mute signal is pulled to ground, the radio over-rides any other audio signal and uses the remote audio signals as the source for output to the speakers. If the radio was OFF when this circuit is pulled low, the radio will turn ON. Additionally, the radio fades the speakers to full front, adjusts the volume to an initial audible level, and sets an AutoTone designed for optimal use with OnStar®. When the mute signal is no longer pulled to ground, the radio returns to the mode it was in previously.
Component Description
Antenna System
The antenna system receives broadcast AM or FM stereo signals from free space and sends the signals to the radio receiver for processing via a coaxial antenna cable. Good antenna grounding is important for good radio reception.
The antenna base and mast should be installed to the torque specifications provided in the Digital Radio Antenna Replacement procedures.
The antenna mast is a single ¼ wave design located at the right front fender.
Ground Strap
The braided ground strap, which is connected between the radio case and the instrument panel fuse block (IPFB), is provided to improve reception and deter noise from entering the audio system.
Radio
The operator interfaces with the radio system through the radio display and controls. Through these controls the operator is able to control system power, volume, fade, balance, bass, and treble equalizations. Control on the integrated CD, MP3, or XM Satellite Radio system is also available when equipped with these options. A vacuum florescent display (VFD) provides system feedback to the operator.
The radio processes the AM and FM signals from the antenna system or the information from the CD media, amplifies that information and sends the output to the speaker system.
The radio is located in the instrument panel (I/P) center stack area and is fastened to the I/P by 2 fasteners. Guide pins are provided to aid in aligning the radio. Electrical connections to the radio are a 24-way connector from the I/P harness, antenna lead connector and braided ground strap. An additional 12-way harness connector is present on OnStar® equipped vehicles. Additional service length is provided in the radio harnesses to allow connection prior to radio installation.
Clock time is displayed continuously on the UM7 and U1C radios when the ignition is OFF. Pressing the RCL provides momentary backlighting. Time is not displayed on the US8 and US9 radios when the ignition is off. Pressing RCL will temporarily display the time.
Radio amplifier outputs to the speakers are protected from damage should speaker leads become shorted to ground or shorted to vehicle power. The radio will sense these conditions and shut down the amplifier outputs in a non-destructive manner. After the short condition is removed, the radio will return to normal operation.
Speakers
The speaker system consists of 4 speakers, mounted in the doors. The optional speaker system (RPO UQ6) includes an additional speaker mounted in the front driver and passenger door mirror trim panel. The premium audio system (RPO WBM) adds a subwoofer and amplifier.
OnStar®
OnStar® equipped (RPO UE1) vehicles use the radio amplifier and speaker system for voice communication from the OnStar® operator to the vehicle. Voice communication from the vehicle to the OnStar® operator is through the OnStar® microphone and module, which is not a part of the radio system.
When OnStar® begins operation, the radio volume is set to a preset level, autotone preset for OnStar® becomes active and the fade control is adjusted to the full front speakers. The radio volume control can then be used to adjust the volume to a desired level.
The radio system and OnStar® system are connected through the 12-way connector at the back of the radio. Left and right channel OnStar® audio, mute control of radio functions by OnStar®, and the audio signal ground are the circuits provided in the 12-way connector.
Disconnecting the 12-way connector from the radio will isolate the radio system from the OnStar® system. Voice communication from the vehicle to the OnStar® operator could be possible under this condition. However, the vehicle occupant will not be able to hear the OnStar® operator.
For more information regarding radio operation problems, refer to Symptoms - Entertainment and Diagnostic Starting Point - Entertainment . For further information regarding OnStar® operation, refer to OnStar Description and Operation .
Amplifier
Vehicles equipped with Premium Audio (RPO WBM) include an amplifier. The amplifier has low level inputs from the radio for the 4 speaker channels and amplifies the sound. The amplifier receives a radio ON signal from the radio. This signal is delayed momentarily at initial key on to prevent any speaker pops during start-up.
The purpose of an 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.
Subwoofer
The premium audio system includes a subwoofer, which is mounted in the rear of the vehicle. The subwoofer is a single speaker, designed for low frequency response. The subwoofer speaker is a dual coil design. The amplifier, which is included with the RPO WBM premium audio package amplifies the low frequency and outputs it to the subwoofer.
Customer Tips
Radio Reception - FM
Select Stations Within Range: The best FM fidelity will be obtained from stations within a 16-64 km (10-40 mile) range. Noise or distortion may become apparent when attempting to receive stations at distances greater than this range.
Suggestion: Reduce treble response when attempting to receive fringe stations.
Tall Structures: Tall buildings or hills may cause degrading or loss of signal. FM stations tend to travel "line of sight." Buildings or hills can interrupt the FM signal.
Suggestion: Reduce treble response.
Interference from another station: Although receiver circuits are among the most advanced type available, there are instances where a radio station can be interfered with by another station.
Suggestion: Select another station or switch to a cassette or CD.
Radio Reception - AM
Static Interference During Weather Disturbances: AM reception is sensitive to storm disturbances such as lightning.
Suggestion: Reduce treble response or select an FM station for weather related information.
Care of Compact Discs
| • | Handle compact discs (CDs) carefully. Touch only the outer edges of the CD or the edge of the hole in the center of the CD. Never touch the glossy side of the CD. Fingerprints and scratches will interrupt the "reading" of the information on the disc. |
| • | Store CDs in their protective cases. Store CDs away from sunlight, dirt, dust, and debris. |
| • | Do not attach a label or tape to a CD. |
| • | Always check for scratches and signs of wear on both sides of the CD. |
| • | Never place any marks on the CD with a marker. |
| • | If a CD becomes contaminated, clean it with a clean, damp, soft, lint-free cloth and mild detergent. Wipe the CD in a straight line from the center hole outward. Do not use cleaning solutions which may damage the CD, such as chemically treated cleaning cloths, benzene, or paint thinners. |
Compact Discs Not Appropriate to Use
These CD players were designed to be compatible with round digital audio CDs with the "Compact Disc Digital Audio" label. Other CDs may be incompatible, causing a no-play condition, excessive skips, "ERR" shown on the radio display or a jam in the loading mechanism. Some incompatible CD types are:
| • | Special-shaped CDs (any that are not round) |
| • | Re-Writeable CDs (CD-RW type are incompatible) |
| • | Recordable CDs (CD-R type are incompatible, except with US8 or US9 radios) |
| • | Library CDs (with thick bar code labels) |
| • | CD with User-applied labels |
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 the FM Broadcaster does not implement RDS properly. |
In some cases, a radio station broadcasting incorrect information may cause the RDS features of the radio to appear to work improperly.
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.
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.
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 |
Technical Information for the MP3/CD Radios (US8, US9)
The US8 and US9 radios will play both standard audio CDs and CD-Rs or CD-RWs. The CD-R/RWs may contain either standard audio (*.cda) or compressed audio (*.mp3).
Customers who record their own music CD-R/RWs should be aware of the following:
| • | The files can be recorded on a CD-R/RW disc with a maximum capacity of 700 MB. |
| • | The radio will play only compressed audio files recorded in the *.mp3 format. It also supports playlists that can be made and saved with popular MP3 software (in the *.m3u format). A playlist name must be no more than 32 characters in length. If the name of a playlist is longer than 32 characters, the radio will ignore the playlist. |
| • | The radio will only play audio from a CD-R/RW, it cannot record audio. |
| • | The radio will play a mixed mode CD-R/RW (one recorded with both *.cda and *.mp3 files). If a mixed mode CD is inserted in the radio,, the radio will assign the standard CD audio to a directory which is listed as ROM audio directory. |
| • | The radio supports multi-session discs, but only the files from the last session will be played. |
| • | There are a total of 20 directories (folders) allowed on a disc. The file structure can be 0-4 directories deep (a folder within a folder, within a folder, etc). Anything more than 20 directories will be ignored. Each directory may have up to 99 files contained within it. Files not having the *.mp3 extension will not be played, but still count toward the maximum. Anything more than the first 99 files within a directory will be ignored. A single disc may have up to 254 files and directories. Anything beyond the 254 limit will be ignored. |
| • | MP3 files must be written to a CD-R/RW in one of the following industry-standard formats: |
| • | ISO 9660 Level 1 |
| • | ISO 9660 Level 2 |
| • | Joliet |
| • | Romeo |
| • | ID3 tag information is displayed by the radio, if available. The ID3 tag information can either be version 1 or 2. The radio will display the filename, song name, artist name, album name, directory name, and playlist name.. |
If the customer does not follow these guidelines when recording a CD-R/RW, the disc may not play in the US8 or US9 radio.
