Cellular System, Entertainment System, and Navigation System: Overview Chevrolet Silverado Classic 2500 HD

Entertainment/Communication Schematic Icons

Entertainment/Communication Schematic Icons Icon Icon Definition IMPORTANT: Twisted-pair wires provide an effective "shield" that helps protect sensitive electronic components from electrical interference. If the wires were covered with shielding, install new shielding. In order to prevent electrical interference from degrading the performance of the connected components, you must maintain the proper specification when making any repairs to the twisted-pair wires shown : The wires must be twisted a minimum of 9 turns per 31 cm (12 in) as measured anywhere along the length of the wires. The outside diameter of the twisted wires must not exceed 6.0 mm (0.2 in)

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Audio Amplifier C1 (UQ7 w/o Y91) Connector Parts Information

Audio Amplifier C1 (UQ7 w/o Y91) Connector Terminal Identification

Test Description

The number below refers to the step number on the diagnostic table.

1. 2: The DTC descriptor indicates which speaker output circuit set the DTC.

DTC B1025, B1035, B1045, or B1055

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step helps to determine if the Diversity Antenna System is operating.

1. 3: This step helps to determine if radio antenna module is receiving the proper signal from the radio.

DTC B1235

Circuit/System Description

The antenna signal circuit is a coaxial cable that carries the radio signal information received by the antenna. The antenna cable also provides a path for DC current for powering the antenna.

The number below refers to the step number on the diagnostic table.

1. 2: This step checks that the VCIM is sending out the proper supply voltage.

DTC B2455

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step tests the condition of the cellular antenna.
2. 3: This step tests the condition of the cellular antenna coax and for proper ground of the cellular antenna.

DTC B2470

The number below refers to the step number on the diagnostic table.

1. 2: This step checks that the VCIM is sending out the proper supply voltage.

DTC B2476

The number below refers to the step number on the diagnostic table.

1. 2: This step tests the at rest state of the keypad signal circuit.

DTC B2482

The number below refers to the step number on the diagnostic table.

1. 3: This step tests for the proper operation of the circuit in the low voltage range.

DTC B2815

The antenna signal circuit is a coaxial cable that carries the radio signal information received by the antenna. The antenna cable also provides a path for DC current for powering the antenna.

The number below refers to the step number on the diagnostic table.

1. 8: If the cellular telephone voice low reference circuit is shorted to voltage the vehicle communication interface module (VCIM) has been damaged and requires replacement.

No (or Noisy) OnStar Audio

The numbers below refer to the step numbers on the diagnostic table.

1. 3: This step determines if the OnStar® status LED has the necessary GREEN LED signal circuit voltage.
2. 5: If the GREEN LED signal is shorted to voltage, then the OnStar® 3-button assembly has been damaged and must be replaced.

OnStar Button LED Inoperative

System Description

This symptom table will enable the user to verify the customer complaint and narrow it to its source. If there is a concern with voice recognition or OnStar® steering wheel control function, technicians should proceed directly to the applicable diagnostic.

OnStar Description and Operation

This vehicle uses the Generation 6.1 version of the OnStar® system. This system consists of the following components

1. Vehicle communication interface module (VCIM)
2. OnStar® button assembly
3. Microphone
4. Cellular antenna
5. Navigation antenna

This system also interfaces with the factory installed vehicle audio system.

Operation of the Hands Free Cellular Phone

Onstar® personal calling (OPC) operates similar to most hand held cellular phones in that the availability for its usage is based on minutes or units. The customer must have a current OnStar® subscription, as this feature cannot be utilized without it. To use OPC, the customer must also purchase units as outlined in the owner's guide provided with the OnStar® system. When the customer purchases minutes, an OnStar® advisor loads these minutes into the vehicle communication interface module (VCIM) over the airwaves at the time of the request, or through a discrete cellular call to the vehicle at a later time. Once loaded into the module, the units may be used for non-international, outbound cellular phone calls, and connection with the OnStar® virtual advisor. Units begin to deplete, 1 unit is equal to 1 minute, as the customer makes outbound phone calls, answers inbound phone calls, or while connected to the OnStar® virtual advisor. In addition, units also have an expiration date, depending upon the type of units purchased. This date is established when the download is performed, and any remaining units expire when the date within the VCIM, which is based on current date and the time transmitted by global positioning system (GPS) satellites, has passed. At any time, the user can press the answer/end call button, say "Units" and verify the number of units remaining.

During a hands free call, the microphone and audio system operate the same way as a standard OnStar® call. When the answer/end call button is pressed, the audio system will mute; the OnStar® system will then return the prompt "OnStar Ready." At this point there are specific commands set to initiate a cellular call. If the vehicle receives a call when the radio is ON, the audio system will mute and an audible ring will be heard though the speakers. The call will be answered when the answer/end call button is pressed.

The VCIM interprets all of the voice-activated commands. A complete list of these commands is supplied in the information provided to the customer. If the information is not available to reference, at any command prompt the caller can say "HELP" and the VCIM will return an audible list of available commands. If the customer concern is not being understood or not being heard by the OnStar® system, the user should place a call to the OnStar® call center to verify proper operation of the microphone. Following this description is an example of the commands and the OnStar® system responses. A complete list of commands is supplied in the information provided to the customer with the OnStar® system.

Mobile Identification Number and Mobile Directory Number

The Generation 6.1 vehicle communication interface module (VCIM) utilizes 2 numbers for cellular device identification, call routing and connection, a mobile identification number (MIN) and a mobile directory number (MDN). The MIN represents the number used by the cellular carrier for call routing purposes while the MDN represents the number dialed to reach the cellular devise. Although technicians have the capability to change these numbers by means of the scan tool, this should ONLY be done at the direction of and with explicit instruction from General Motors Technical Assistance Center (GM TAC).

Operation of the OnStar® Speech Recognition Systems

OnStar® Generation 6.1 users communicate with 2 speech recognition systems. Speech recognition allows the user to speak to one computer in the vehicle, and one reached over a phone line. The computer tries to understand the users command, and responds by speaking back, or by taking the appropriate action, e.g. dialing the phone.

1. Personal Calling uses a speech recognition system that resides in the vehicle. When the user presses the dot button, the system states, Ready, and listens for the user's command. The user can speak commands to control the hands-free phone.
2. Virtual advisor is a remote speech recognition system that the caller access by making a phone call. The user connects to virtual advisor by requesting it during personal calling use. The user is then transferred to the virtual advisor server and talks to it via a cellular connection.

The OnStar® speech recognition systems use speech technology that is designed to understand a wide range of American English speakers. Although there is no one right way to speak English, the system will work best when users try to modify their pronunciation should they encounter difficulty. Users who do not obtain good results are advised to try the tips and workarounds found in this section.

General Tips for Better Speech Recognition

Personal Calling Commands

Radio/Audio System Description and Operation

The Entertainment System on this vehicle is configured with a radio, antenna, and speakers.

The following list shows the radios available for this vehicle

1. Radio (UM7) - AM/FM with Cassette
2. Radio (UB0) - AM/FM with CD
3. Radio (UB1) - AM/FM, Cassette and CD
4. Radio (UC6) - AM/FM, Integral Multi Disc CD Changer

Radio Features

Cassette Features

Compact Disc Features

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

1. AM/FM Reception
2. Voice Recorder (Travel Note)
3. Audio Amplifier
4. Theft Deterrent
5. Integral Multi Disc CD Changer (IMDX)
6. Remote Playback Device
7. Radio Data System (RDS)
8. Tape/CD Player Error Messages
9. Rear Seat Audio (RSA)
10. XM Satellite Radio