This vehicle uses the Generation 5 version of the OnStar® system. This system consists of the following components:

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

The vehicle communication interface module (VCIM) is a 3-watt cellular device that allows the user to communicate data and voice signals over the national cellular network. It is powered by a fused, battery positive voltage circuit, connected through vehicle wiring to the 3-button assembly and the radio, and attached by means of coax cables to the cellular and navigation antennas. Ground for the module is accomplished by means of dedicated circuits that are routed with body wiring systems to chassis ground points. The module houses 2 modems, one to process global positioning system (GPS) data, and the other for cellular information. Satellites orbiting earth are constantly transmitting signals of their current location, from which the OnStar® system is able to pinpoint its own location. The navigation antenna receives these GPS signals and provides the data to the VCIM to be processed. The VCIM communicates with the rest of the vehicle over the class 2 serial data bus. Ignition state is determined by the VCIM through class 2 messaging. The module also has the capability of commanding the horn, door lock/unlock and operating the exterior lamps using the class 2 serial data circuit. When an OnStar® keypress is made, a class 2 message is sent to the audio system to mute all radio functions and transmit OnStar® originated audio. After the audio system is muted, the OnStar® signals are transmitted to the audio system on the cellular telephone voice signal circuit, and returned to the module on the cellular telephone voice low reference circuit. The cellular modem connects the OnStar® system to the cellular carrier's communication system by interacting with the national cellular infrastructure. The module sends and receives all cellular communications over the cellular antenna and cellular antenna coax.

The OnStar® button assembly may be part of the rearview mirror on some vehicles or a separate unit on others. The button assembly is comprised of 3 buttons and a status LED. The buttons are defined as follows:

The OnStar® button assembly receives 10 volts on the keypad supply voltage circuit. When pressed, each button completes a circuit across a resister allowing a specific voltage to be returned to the vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.

The OnStar® status LED is located to the right of the emergency button on a mirror-mounted assembly and to the left of the answer/end call button when the assembly is mounted on the dash or overhead console. The LED is green when the system is on and operating normally. A green and flashing LED is an indication that a call is in progress. A red LED indicates a system malfunction. If a system malfunction is present but the OnStar® system is still able to make a call, the LED will flash red during the call.

The OnStar® LED is controlled by the VCIM over the keypad red LED signal circuit and the keypad green LED signal circuit.

The OnStar® cellular microphone can be part of the rearview mirror assembly, or on some vehicle lines the microphone can be a separate, stand-alone unit. In either case, the microphone is supplied voltage on the cellular microphone signal circuit, while voice data is sent back to the vehicle communication interface module (VCIM) by means of either a cellular microphone low reference circuit or by a drain wire.

This vehicle can be equipped with separate cellular and navigation antennas or with a combination antenna, which brings the functions of both into a single part.

The cellular antenna is the component that allows the OnStar® system to send and receive data over airwaves by means of cellular technology. This antenna is connected at the base to a coax cable that plugs directly into the vehicle communication interface module (VCIM). The navigation antenna is used to collect the constant signals of the orbiting satellites. Within the antenna is housed a low noise amplifier that allows for a more broad and precise reception of this data. Current global positioning system (GPS) location is collected by the module every time a keypress is made. The OnStar® Call Center also has the capability of pinging the vehicle during an OnStar® call, which commands the module to retrieve the latest GPS location and transmit that location to the OnStar® Call Center. A history location of the last recorded position of the vehicle is stored in the module and marked as aged. In the event the VCP loses or is removed from power, this history location is used by the OnStar® Call Center as a default. Actual GPS location may take up to 10 minutes to register in the event of a loss of power. This antenna requires a clear and unobstructed path to the satellites in the sky. Window tinting on vehicles may interfere with the GPS sensor functions, depending upon the amount of darkening and/or metallic particles that are embedded in the film of the tinting material.

The OnStar® system uses a unique sleep cycle to allow the system to receive cellular calls while the ignition is in the OFF position. This cycle enables the vehicle communication interface module (VCIM) to perform remote functions, such as door unlock, as commanded by the OnStar® Call Center and to maintain an acceptable level of battery electrical drain.

The OnStar® system uses 3 states of readiness:

The High power state is in effect whenever the ignition is in the ON or RUN position, and enables the OnStar® system to send and receive cellular calls and to perform all remote functions.

The Low power state is entered when the vehicle ignition is placed in the OFF position and the retained accessory power (RAP) function has been turned off or times out. This state will last for one minute and allows incoming cellular calls to be received.

After one minute, the OnStar® system moves to the Sleep state. This state will not recognize or receive incoming cellular calls.

At a predetermined time of up to 9 minutes, which is recorded within the VCIM, the system re-enters the Low power state for one minute to listen for calls from the OnStar® Call Center. After this interval, the system will again return to the Sleep state for 9 minutes.

This process will continue for up to 48 hours, after which the OnStar® system will permanently enter the Sleep state until the ignition is once again turned to the ON or RUN position.

In the event the OnStar® system loses power, or is temporarily removed from battery power, the system remains in the Sleep state as long as the key in the OFF position. The system will not begin to cycle until the vehicle, with the ignition ON, passes into an open outside area where a global positioning system (GPS) signal can be acquired, providing a reference for time. The OnStar® Call Center maintains a record of the time each vehicle enters the one-minute Low power state by synchronizing the Call Center clocks with those of the vehicle, based on the GPS signals.

If a customer has not renewed an OnStar® account after expiration, OnStar® will make a discrete cellular call to the vehicle to deactivate the OnStar® system. Before taking this action, the customer is notified that the OnStar® system in that vehicle will be deactivated unless the customer renews the account. After the vehicle has been successfully deactivated, the customer will experience the following conditions when attempting to contact OnStar® from that vehicle:

When an OnStar® system is successfully deactivated, the system will NOT attempt to connect to the OnStar® Call Center following a collision or front air bag deployment.

Within the vehicle communication interface module (VCIM) is a set of unique numbers that identify the OnStar® customer and the specific vehicle where the module resides. These numbers, the station identification number (STID) and the electronic serial number (ESN), are transmitted over the cellular network following an OnStar® keypress and are essential for proper identification and connection to the OnStar® Call Center. In the event the VCIM requires replacement, perform the OnStar® reconfiguration procedure. This procedure allows for the new STID and ESN to overwrite the old numbers and update customer and vehicle information at the OnStar® Call Center. The Reconfiguration process is explained within the VCIM replacement procedure, or the OnStar® Reconfiguration Procedure. Refer to Communication Interface Module Replacement or to OnStar Reconfiguration .

The proper operation of the OnStar® System is dependent on several elements outside the components integrated into the vehicle. These include the National Cellular Network Infrastructure, the cellular telephone carriers within the network, and the global positioning system (GPS).

The cellular operation of the OnStar® system may be inhibited by factors such as the user's range from an analog cellular tower, the state of the cellular carriers' equipment, and the location where the call is placed. Making an OnStar® keypress in areas that lack sufficient cellular coverage or having a temporary equipment failure may result in the inability to connect to the OnStar® Call Center. The OnStar® system may also experience connection issues if the identification numbers for the module, station identification number (STID), and electronic serial number (ESN), are not recognized by the cellular carrier's local signal receiving towers. Issues such as these require the assistance of the General Motors Technical Assistance Center OnStar® Group, which coordinates with cellular carriers to resolve connection issues.

The satellites that orbit earth providing the OnStar® system with GPS data have almost no failures. In the event of a no GPS concern, the failure will likely be one of the following:

During diagnostic testing of the OnStar® system, the technician should ensure the vehicle is located in an area that has a clear unobstructed view of the open sky, and preferably an area where analog cellular calls have been successfully placed. These areas can be found by successfully making an OnStar® keypress in a known good OnStar® equipped vehicle and confirming success with the OnStar® Call Center advisor. Such places can be used as a permanent reference for future OnStar® testing.

The hand-free, OnStar® Personal Calling (OPC) cellular phone feature is an additional option to the OnStar® system. This feature is already embedded within the vehicle communication interface module (VCIM), however this feature must be activated by an OnStar® advisor. This is done most often during the initial OnStar® configuration, if the home location of the vehicle is in a geographic area where OPC is available. In the event this feature is not enabled, customers may connect to the OnStar® Call Center by pressing the blue OnStar® button and asking an advisor if OPC is available in their area. Users of the Generation 5 OnStar® system can verify that the system has been configured for OPC by following these simple steps:

1. Press the answer/end call button
2. Wait for the system to respond "OnStar® Ready"
3. Speak the word "Dial"

If the system responds "Phone Unavailable" the system has not been configured for OPC. All other responses confirm that OPC has been enabled.

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 for this feature to work. To use OPC, 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 vehicle communication interface (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 are used under the following conditions:

In addition, units also have an expiration date, depending upon the type of units purchased. This date is established during download and any remaining units expire when the date within the VCIM has passed. At any time, the user can press the answer/end call button, say the word "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 which will 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, 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.

Some vehicles equipped with the OnStar® system have the capability of accessing voice mailboxes and other automated phone systems on the steering wheel controls, while the OnStar® Personal Calling (OPC) feature is in use. Depending of the vehicle, if the Talk or Mute button on the steering wheel controls is depressed during an OPC call, the vehicle communication interface module (VCIM) receives the message on the class 2 serial data bus from either the radio, driver information module, or body control module (BCM). This message is interpreted as a request to turn any spoken numbers into dual tone multi-frequency (DTMF) tones to be delivered over the airwaves to the requested phone system. Complete instructions for operation of these features can be found in the information provided to the customer with the OnStar® system.

The steering wheel controls are a resistor network that consist of multiple momentary contact switches and a series of resistors. The switches and resistor network are arranged so that each switch has a different resistance value. When a switch is pressed, a voltage drop occurs in the resistor network, which produces a specific voltage value unique to the switch selected, to be interpreted by either the radio, driver information module, or BCM.

The following is an abbreviated list of features that may have an impact for the technician when servicing or diagnosing an OnStar® system. For a full list of OnStar® Personal Calling (OPC) features, consult the owners guide provided to the customer with the OnStar® system.

Voice Feedback

The OnStar® Personal Calling (OPC) system has the capability of responding to the user with either an automated voice response or with a tone. These 2 types of responses can be switched back and forth by pressing the answer/end call button, waiting for the system to respond "OnStar® Ready" and speaking the phrase "Voice feedback". The system will then respond, "Voice feedback is now on/off".

OPC Security/System Lock

Customers have the capability to lock their OnStar® Personal Calling (OPC) system by pressing the answer/end call button, speaking the word "Security", and entering a 4-digit code. Once this process is complete, the user must enter the code before OPC is available. In the event the customer cannot remember his code and is unable to use his system, he can press the blue OnStar® button and speak to an advisor to unlock the system via a discrete cellular call to the vehicle.

Nametags

Customers have the ability to store telephone numbers within the module, referenced by a nametag for the convenience of frequently dialed numbers. This process is initiated by pressing the answer/end call button, waiting for the system response, then speaking the response "Store". The system will respond with "Number please" at which time the user should enter the number desired to be stored. Once complete, saying the word "Store" again lets the system know you are finished entering the number. At this time, the system will elicit the user to assign a "Nametag" to that number. From this point forward, the user can dial this number by initiating the OnStar® Personal Calling (OPC) feature, speaking the word "Call", and repeating the nametag assigned. To delete a nametag, the user should initiate OPC, say "Delete" then speak the nametag to be removed. In the event a nametag cannot be deleted in spite of repeated attempts from several speakers, the OnStar® module will require replacement.

Mobile Identification Number and Mobile Directory Number

The Generation 5 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 the General Motors Technical Assistance Center (GM TAC).

OnStar® Generation 5 users communicate with 2 speech recognition systems. Speech recognition allows the user to speak to the computer in the vehicle and the 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, such as dialing the phone.

The OnStar® speech recognition systems uses speech technology that understands a wide range of American English speakers. However the system will work best when users enunciate clearly. Users who do not obtain good results are advised to try the tips found in this section.