The entertainment system on this vehicle may have several different configurations available to it. To determine the specific configuration of the vehicle, please see the Service Parts ID Label, and refer to
RPO Code List.
The entertainment system on this vehicle is configured with either a base or an uplevel system. The base and uplevel systems each contain a radio, antenna, speakers, and on some systems 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, programmable equalizer (EQ), and digital satellite radio (U2K).
Each item in the list below represents topics covered in detail below.
• | Radio Circuit Operation |
Radio Circuit Operation
Radio Power
The radio is supplied power by a fused B+ circuit. The radio does not use a discrete ignition feed circuit for power moding. The power mode master (PMM) provides the system power mode to the radio via serial data messages. The PMM determines the system
power mode by processing power mode information from ignition switch inputs. Serial data power modes supported by the radio are OFF, ACCESSORY, RUN, and CRANK REQUEST.
Radio Grounds
The vehicle harness provides a ground for the radio circuits. The radio may also be case grounded.
Radio Data Link Communication
The radio communicates with other modules via serial data.
Radio Outputs
At minimum volume, the plus (+) and minus (-) speaker outputs are approximately half battery voltage, measured to vehicle ground. As the volume increases, the plus and minus change to create a voltage difference between each other either driving the voice
coil of the speaker, or being fed to an amplifier.
Radio Head Dimming
Dimming and backlighting levels are determined by the serial data messages the radio receives.
Antenna System
Fixed Mast Antenna
The fixed mast antenna can withstand most car washes without being damaged. If the mast should ever become slightly bent, straighten it out by hand. If the mast is badly bent, replace it.
Check occasionally to make sure the mast is still tightened to its base. If tightening is required, tighten by hand, then with a wrench one quarter turn.
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 |
• | 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:
• | 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 miles).
FM Reception
The shorter wavelengths of the higher frequency FM band:
• | 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 miles). 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 |
Speaker Operation
Speakers turn electrical energy into mechanical energy to move air, using a permanent magnet and an electromagnet. The electromagnet is energized when the radio or amplifier (if equipped) delivers current to the voice coil on the speaker. The voice coil
will form a north and south pole that will cause the voice coil and the speaker cone to move in relation to the permanent magnet. The current delivered to the speaker is rapidly changing alternating current (A/C). This causes the speaker cone to move in two
directions producing sound. When the speaker is at rest, such as when the volume at a minimum value, the voltage applied to each side of the speaker is ½ ignition system voltage. This way, the speaker cone can be moved in either direction.
Radio Error Messages
The Radio may display the following Error Messages (Not all messages may be applicable):
• | ERR: This message is displayed when the radio is unable to play the inserted cassette or CD |
• | LOC: This message is displayed when the radio has entered Theft mode. |
• | CAL/CAL ERR: This message is displayed when the radio has detected an invalid calibration. |
• | CDX ERR: Displays if communication is lost with the remote CD changer. |
• | CHECK CD: Displays when the player encounters a focus or tracking error. |
• | CHK CDXX: Displays when the CD changer encounters a focus or tracking error. |
• | CHK TAPE: Displays if a tape has been inserted but is unable to be played due to an error. |
• | DOOR OPEN: Displays when the CD changer door has been left open. |
• | NO DISC: Displays when the radio expected a disc to be inserted. |
• | NONE: Displays when the radio is unable to detect the vehicle speed data information via the serial data circuit. |
If an error message is displayed, perform the appropriate diagnostics.
Theft Deterrent
The radio theft deterrent system is intended to disable or limit 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 via serial data. A possible cause of incorrect VIN info could be the radio was originally installed in another vehicle.
The radio has the following theft operating modes as part of the theft deterrent system:
• | 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. |
• | No VIN Mode--A radio that has not received or learned a VIN. In this mode the radio has limited 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. |