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. 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® 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.
OnStar® Microphone
The OnStar® 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:
Separate, standalone cellular and navigation antennas
A combination cellular and navigation antenna, which brings the functions of both into a
single part
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® 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® 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 it
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 location of the GPS antenna and the amount of
2007 Hummer H3
2007 ACCESSORIES AND EQUIPMENT Cellular, Entertainment and Navigation - H3