Hummer H2. Manual — part 223

Vehicle Communication Interface Module (VCIM)

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 the 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(R) 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. The ignition state is determined by the VCIM through class 2 messaging. The module
also has the capability of commanding the horn, initiating door lock/unlock and operating the exterior lamps
using the class 2 serial data circuit. When an OnStar(R) keypress is made, a class 2 message is sent to the audio
system to mute all radio functions and transmit OnStar(R) originated audio. After the audio system is muted, the
OnStar(R) 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(R)
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.

OnStar(R) Button Assembly

The OnStar(R) 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:

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The answer/end call button, which is black with a white dot allows the user to answer and end calls or
initiate the personal calling feature, if equipped.

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The blue OnStar(R) call center button, which displays the OnStar(R) logo, allows the user to connect to
the OnStar(R) call center.

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The emergency button, which will display either a red or white cross, sends a high priority emergency
call to the OnStar(R) call center when pressed.

The OnStar(R) 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(R) 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. When the status LED is green and flashing, it is an
indication that a call is in progress. When the LED is red, this indicates a system malfunction is present. In the
event there is a system malfunction and the OnStar(R) system is still able to make a call, the LED will flash red
during the call. The OnStar(R) LED is controlled by the VCIM over the keypad red LED signal circuit and the
keypad green LED signal circuit.

OnStar(R) Microphone

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2004 ACCESSORIES & EQUIPMENT Cellular Communication - Hummer H2

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

Cellular and Navigation Antennas

This vehicle will be equipped with one of the following types of antennas:

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Separate, standalone cellular and navigation antennas.

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A combination cellular and navigation antenna, which brings the functions of both into a single part.

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A cellular, navigation, and digital radio antenna, which also incorporates the functionality of the digital
radio receiver satellite and terrestrial antennas (XM).

The cellular antenna is the component that allows the OnStar(R) 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. The current global positioning system (GPS) location is collected by
the module every time a keypress is made. The OnStar(R) Call Center also has the capability of pinging the
vehicle during an OnStar(R) call, which commands the module to retrieve the latest GPS location and transmit
it to the OnStar(R) 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(R) 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 location of the GPS
antenna and the amount of darkening and/or metallic particles that are embedded in the film of the tinting
material.

OnStar(R) Sleep Cycle (Generation 5)

The OnStar(R) 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 over the air by the OnStar(R) Call Center, when
requested by the customer, and to continue to maintain an acceptable level of battery electrical drain.

The OnStar(R) system uses 3 states of readiness:

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High power

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Low power

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Sleep

The high power state is in effect whenever the ignition is in the ON or RUN position, and enables the OnStar(R)
system to send and receive cellular calls and perform all remote functions. The low power state is entered once
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 1 minute and allows incoming cellular calls to be received.

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2004 ACCESSORIES & EQUIPMENT Cellular Communication - Hummer H2

After the 1 minute window, the OnStar(R) system moves to the sleep state. This state will not recognize or
receive incoming cellular calls. At a predetermined time recorded within the VCIM, up to 9 minutes, the system
re-enters the low power state to listen for a call from the OnStar(R) Call Center for 1 minute. After this interval,
the system will again return to the sleep state for 9 minutes. After these 9 minutes, the system will again enter
the low state of power and listen for any incoming calls that the OnStar(R) Call Center may be sending. In the
event a call is being sent, the OnStar(R) system will receive the call and immediately go into the high power
mode to perform any requested functions. If no call is received during the 1 minute interval, the system will go
back into the sleep mode for another 9 minutes. This process will continue for up to 48 hours, after which, the
OnStar(R) 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(R) system loses, or is temporarily removed from battery power, the system will remain
in the sleep state while the key in the OFF position. It will not begin to cycle until the vehicle passes into an
open outside area with the ignition ON, where a global positioning system (GPS) signal can be acquired,
providing a reference for time. The OnStar(R) Call Center is able to maintain a record of exactly what time each
vehicle will enter the one minute low power state by synchronizing their clocks with those of the vehicle, based
on GPS signals.

OnStar Sleep Cycle (Generation 6)

The OnStar(R) Generation 6 system uses a different sleep cycle than the Generation 5 system 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
over the air by the OnStar(R) Call Center, when requested by the customer, and to continue to maintain an
acceptable level of battery electrical drain.

The OnStar(R) Generation 6 system varies by what type of cellular market it is in. If the vehicle is parked in an
analog service only market, the sleep cycle works exactly the same as a Generation 5 system (see above). In a
digital service market, the system uses the following 3 power modes when the vehicle is turned off:

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High Power

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Digital Standby

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Sleep

The high power state is in effect whenever the ignition is in the ON or RUN position, and enables the OnStar(R)
system to send and receive cellular calls and perform all remote functions. The digital standby power state is in
effect after the vehicle has been shut off and the retained accessory power (RAP) has timed out. When in digital
standby mode, the OnStar module is able to perform all remote functions as commanded by an OnStar advisor
at any time, for a continuous 8 hours. After 8 hours, the OnStar module will follow the standard sleep state that
a Generation 5 module uses (9 minutes off, 1 minute of digital standby, based on the time of the GPS signals).

In the event the OnStar(R) system loses, or is temporarily removed from battery power, the system will remain
in the sleep state while the key in the OFF position. It will not begin to cycle until the vehicle passes into an
open outside area with the ignition ON, where a global positioning system (GPS) signal can be acquired,
providing a reference for time. The OnStar(R) Call Center is able to maintain a record of exactly what time each
vehicle will enter the one minute low power state by synchronizing their clocks with those of the vehicle, based
on GPS signals.

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2004 ACCESSORIES & EQUIPMENT Cellular Communication - Hummer H2

Deactivated OnStar(R) Accounts

In the event a customer has not renewed their OnStar(R) account after expiration or the account was never
activated, OnStar(R) will make a discrete cellular call to the vehicle to deactivate the OnStar(R) system. Before
taking this action, customers are notified that the OnStar(R) system in their vehicle will be deactivated unless
they elect to renew the account. After the vehicle has been successfully deactivated, customers will experience
the following when attempting to contact OnStar(R) from their vehicle:

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During an OnStar(R) Call Center button press, the customer will be connected to a dedicated sales team
who can sell an OnStar(R) subscription and reactivate the vehicle. Depending on the type of OnStar(R)
hardware in the vehicle, the customer may first hear a demonstration message stating there is no current
OnStar(R) subscription for the vehicle, and directing the customer what to do to activate services.

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During an emergency button press, a demo message will be played indicating the service has been
deactivated.

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OnStar(R) personal calling (OPC) will not be available, as this feature requires the customer to have a
current OnStar(R) account. Attempts to use this feature may result in cellular connection failure messages
and the inability to connect to the number dialed.

It is of particular note, that when an OnStar(R) system is successfully deactivated, it will NOT attempt to
connect to the OnStar(R) Call Center in the event of a collision or if the vehicles front air bags deploy for any
other reason.

Certain vehicles that have never had an active OnStar(R) account, that have been deactivated, may be unable to
establish a connection with the OnStar(R) Call Center. When normal published diagnostic procedures do not
indicate a possible cause for the no connect concern, the vehicle may have been deactivated. For deactivated
vehicles, a no connect response should be considered normal operation. Further diagnosis and subsequent repair
is only necessary should the customer elect to become an active OnStar(R) subscriber.

OnStar(R) Reconfiguration Procedure

Within the vehicle communication interface module (VCIM) are a set of unique numbers that identify the
OnStar(R) customer and the specific vehicle the module resides in. These numbers, the station identification
number (STID) and the electronic serial number (ESN) are transmitted over the cellular network when an
OnStar(R) keypress is made and are essential for proper identification and connection to the OnStar(R) Call
Center. In the event the VCIM requires replacement, the OnStar(R) reconfiguration procedure must be
performed. This procedure allows for the new STID and ESN within the replacement module to overwrite the
old numbers and update customer and vehicle information at the OnStar(R) Call Center. The reconfiguration
process is explained within the VCIM replacement procedure, or the OnStar(R) Reconfiguration Procedure
found in the Cellular Communication diagnostic information and procedures section.

OnStar(R) Cellular, GPS, and Diagnostic Limitations

The proper operation of the OnStar(R) 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) system.

The cellular operation of the OnStar(R) system may be inhibited by factors such as the user's range from an

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2004 ACCESSORIES & EQUIPMENT Cellular Communication - Hummer H2