Chevrolet Silverado / GMC Sierra. Service manual — part 2252

Additionally, the radio fades the speakers to full front, adjusts the volume to an initial audible
level, and sets an Auto Tone 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.

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 VFD (vacuum florescent display) 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 center stack area and is fastened to the instrument
panel by fasteners. A rear bullet type guide pin is provided to aid in aligning the radio. An
electrical connection to the radio is a 30-way connector that is part of the I/P harness, antenna
lead connector, and an additional 16-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.

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.

UVA Radio

The UVA radio is a dual play radio that supports the playback of CDR, CDR/W and CDROM
media with software decoders for MP3 format.

Speakers

The base model speaker system consists of six speakers. Four 6-inch speakers are mounted in each

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Cellular, Entertainment, and Navigation - Cab & Chassis Sierra, Cab & Chassis

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of the doors. Two 1-inch tweeter speakers are mounted in the A-pillars. The uplevel speaker
system adds two 1-inch tweeter speakers are mounted in the D-pillars, subwoofer and an
amplifier.

Auxiliary Jack Socket

The AM/FM Stereo CD radio shall provide a 3.5 mm Auxiliary stereo jack that will allow
playback of audio signals from remote devices (e.g., portable tape player, portable CD player or
MP3 playback device, etc.).

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, auto tone 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 16-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 16-way connector. Disconnecting the 16-
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.

Theft Deterrent

The radio theft deterrent system is intended to disable radio functionality if incorrect vehicle
information is received by the radio. The radio disables functionality if the VIN information
received by the radio does not match the VIN information that has been learned by the radio. A
VIN sequence is the last 6 digits of the VIN. The radio receives this information in a GMLAN
frame form.

The radio shall provide the following theft operating modes as part of the radio theft deterrent
system:

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No VIN Mode-A radio that has not received or learned a VIN. In this mode the radio has
limited functionality.

Normal Mode-A radio has received a VIN sequence. The radio only learns the VIN
sequence if the VIN sequence contained all 6 digits. In this mode the radio has full
functionality.

Theft Detected Mode-A radio that had previously learned a VIN sequence and subsequently
received a VIN sequence not matching the learned sequence. In this mode the radio has
limited functionality.

Customer Tips

Radio Reception FM

The best FM fidelity will be obtained from stations within 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 buildings or hills may cause a degraded or lost signal. FM signals tend to travel "line of
sight". Suggestion: Reduce treble response around tall buildings.

Although receiver circuits are among the most advanced type available, there are instances
where one radio station can interfere with another station. Suggestion: Select another station
or switch to a cassette or CD.

Radio Reception AM

AM reception is sensitive to storm disturbances such as lightning. Suggestion: Reduce treble
response or switch to FM.

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

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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, and "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

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

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