Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS .
OnStar Steering Wheel Control Functions Inoperative
Some vehicles equipped with the Onstar® system have the capability of accessing voice mailboxes and other automated phone systems by means of the steering wheel controls, while the Onstar® Personal Calling (OPC) feature is in use. If the "Talk" or "Mute" button (depending upon the vehicle) on the steering wheel controls are depressed during an OPC call, the Vehicle Communication Interface Module receives the message on the Class 2 serial data bus from either the radio, driver information module, or body control module. 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 phone system the user is communicating with. 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, dash integration module, or body control module. In the event the Onstar® steering wheel control functions are inoperative, technicians should refer to DIAGNOSTIC SYSTEM CHECK-ENTERTAINMENT SYSTEM to begin diagnosis of the steering wheel control concern.
Vehicle Communication Interface Module (VCIM)
The 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 two modems, one to process GPS data, and the other 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 Vehicle Communication Interface Module 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 in made, a class 2 message is sent to the audio system to mute all ratio functions and transmit Onstar® originated audio. After the audio system is muted, the Onstar® signal 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.
Onstar® Microphone
The Onstar®, or cellular, microphone can be part of the rear view mirror assembly or, on some vehicle lines, can be a separate, standalone 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 VCIM by means of either a cellular microphone low reference circuit or a drain wire.
This vehicle will be equipped with either separate cellular and navigation antennas, or a combination Cellular and Navigation 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. 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 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 amount of darkening and/or metallic particles that are embedded in the film of the tinting material.
Onstar® Reconfiguration Procedure
Within the Vehicle Communication Interface Module are a set of unique numbers that identify the Onstar® 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® keypress is made and are essential for proper identification and connection to the Onstar® Call Center. In the event the VCIM requires replacement, the Onstar® 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® Call Center. The Reconfiguration process is explained within the Vehicle Communication Interface Module replacement procedure.