Battery positive voltage is provided to the radio from the Radio (15A) fuse in the fuse block. The radio is grounded through a braided cable case ground. The radio is enabled/disabled by class 2 messages from the body control module (BCM). The entertainment system on this vehicle is configured with a base and uplevel system. The base and uplevel systems contain a radio, antenna, speakers, and on some vehicles an audio amplifier.

The uplevel system differs from the base system by providing the customer with enhanced audio system features. Some of those features may include the radio data system (RDS), an audio amplifier, and programmable equalizer (EQ). Satellite digital radio (U2K) is available with the uplevel systems.

The following list shows the audio system RPOs available with this vehicle:

Each item in the following list represents topics covered in detail below:

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:

AM Reception

The AM band has a lower frequency range than the FM band. These longer wavelengths:

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:

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:

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 a fixed mast which is mounted on the body of the vehicle. Mast antennas are typically located on the fender or rear quarter panel of the vehicle.

Audio Amplifier

The purpose of the amplifier is to increase the power of a voltage or current signal. The output signal of an amplifier may consists 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 midrange amplifier.

When the radio is turned ON, it sends a voltage signal to the audio amplifier via the radio on signal circuit. The gain control signal circuit allows the radio to recognize that the amplifier is present. Once the radio detects the amplifier, the radio will output low-level signals to the amplifier. With the amplifier enabled, the signal that drives the speaker is now amplified.

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:

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.

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

In some cases, a radio station broadcasting incorrect information may cause the RDS features of the radio to appear to work improperly.

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.