Cellular Communication System: Overview GMC Yukon II

Test Description

The numbers below refer to the step number(s) on the diagnostic table.

1. 2: Lack of communication may be due to a partial malfunction or a total malfunction of the class 2 serial data circuit. The specified procedure will determine the condition.
2. 5: The presence of DTCs which begin with "U" indicate some other system control module is not communicating.

Diagnostic System Check - Cellular Communication

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

1. 2: This step tests for proper ground on the navigation antenna.
2. 3: This step tests the condition of the navigation antenna.

DTC B2462

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

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

DTC B2476

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

1. 2: By disconnecting the VCU you can check the 3 wire bus supply and carrier voltages supplied by the VIU.

DTC U1500

System Description

This symptom table will enable the user to verify the customer complaint and narrow it to its source. If the OnStar® system is always on, regardless of ignition state or if there is a concern with voice recognition or the remote actuated features of the OnStar® system, technicians should proceed directly to the applicable diagnostic found in Symptoms - Cellular Communication .

This procedure is for diagnosing problems with the OnStar® button assembly. The following numbers refer to the steps in the table.

1. 3: Determines if the OnStar® status LED has the necessary GRN LED signal circuit.
2. 5: If the GRN LED signal is shorted to voltage then the OnStar® three button assembly has been damaged. The OnStar® three button assembly has to be replaced.

OnStar Button LED Inoperative

OnStar Description and Operation

This vehicle will be equipped with either the 2.0 or 2.6 version of the OnStar® system. Both systems consist of a vehicle interface unit (VIU), vehicle communication unit (VCU), GPS antenna, cellular antenna, microphone and OnStar® button assembly. Both the systems interface with the vehicle audio system.

The OnStar® system version 2.0 provides the customer with impact detection, navigation instructions, emergency services, stolen vehicle tracking and recovery service, roadside assistance, door unlock, light flash and horn pulse.

The OnStar® system version 2.6 provides all the same features as version 2.0 with the addition of a hands free cellular phone. The OnStar® Personal Calling feature, if equipped, uses voice commands for dialing and programming.

Operation of the Hands Free Cellular Phone

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 OnStar® Personal Calling, the customer must also purchase units as outlined in the owners guide provided with the OnStar® system. When the customer purchases minutes, an OnStar® advisor "loads" these minutes into the VIU or 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 (one unit is equal to one 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 VIU or VCIM (which is based on current date and time transmitted by 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 "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 or VIU interpret 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 or VIU 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

Directives by the Federal Communication Commission (FCC) have mandated that cellular devices manufactured after November 2002 must have a capability that allows customers to transfer their assigned phone numbers to any new cellular devises purchased in the future. Devises which fall into this category no longer have a single "phone number" but two numbers which identify that device, a MIN (Mobile Identification Number) and a MDN (Mobile Directory Number). 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. Because of these FCC directives, some OnStar systems may not recite the correct phone number when the user requests the "My Number" feature of OPC. This situation is considered normal for any OnStar system that exhibits the condition. Customers using OPC can contact the OnStar Call Center and ask an advisor what their correct number is at any time. 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 the General Motors Technical Assistance Center (GM TAC).

Dialing a Phone Number Hands Free

Operation of the OnStar® Speech Recognition Systems

OnStar® Generation 2.6 users communicate with two 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 user's 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