Module Information - Component
Serial #8-11: This is the first partition of the serial number.
Serial #12: This is the second partition of the serial number.
Serial #13-16: This is the third partition of the serial number.
Serial # 17-18: This is the last partition of the serial number.
Module Information - 3 Watt Transmitter ID: This displays the part number for the transmitter.
Module Information - 8-Digit GM Part
Number: This displays the part number for the VIU.
Module Information - Julian Date Of Build: This displays the day of the year the module was built.
Module Information - Master Flash ROM ID: This displays the calibration or program revision level used in the Master ROM.
Module Information - PROM ID: This displays the 4-digit number of the PROM incorporated into the driver door module (DDM).
Module Information - Year Module Built: This displays the 4-digit year of build.
Module Information 2 - Electronic Serial
Number: This display the 6-8 digit numeric order in which the module was built.
Module Information 2 - VIU Station ID: This displays an alpha-numeric ID of the VIU manufacturing station.
Slave Flash ROM ID: This displays the calibration or program revision level used in the Slave ROM.
Scheme 99
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS .
VCU or VIU Reprogramming
Important: The new OnStar® component parts must be installed prior to the reconfiguration of the OnStar® system.
After replacement of the vehicle communication unit (VCU) or vehicle interface unit (VIU), the OnStar® system must be reprogrammed.
- Press and hold the Answer/End Button on the OnStar® Button Assembly until the System Status Light goes from solid GREEN to RED and back to GREEN again.
- Call the OnStar® Call Center at 1-888-OnStar1, select prompt 1.
- Give the operator the Electronic Serial Number (ESN) off the new VCU or the Station ID (STID) number off the VIU.
- Move the vehicle outside and let the vehicle run for 10 minutes.
- Press the OnStar® Call Center Call button and ask for a "Reconfiguration".
Scheme 100
- Remove the I/P trim panel. Refer to «TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER»(ref-176702-S10596506242005051000000) .
- Lower the front of the headliner.
- Disconnect the cable connector (3) from the VCU.
- Disconnect the cable connector (1) from the antenna base.
- Remove the six cable clips (2) from the A-pillar.
- Remove the cable from the vehicle.
Vehicle Interface Unit (VIU)
The Vehicle Interface Unit (VIU) is powered by a fused battery positive voltage circuit, connected through vehicle wiring to the 3 button assembly, radio, microphone and the Vehicle Communication Unit. It is also attached by means of a coax cable to the GPS antenna. Ground for the module is accomplished by means of dedicated circuits that are routed with body wiring systems to chassis ground points.
The VIU also houses the cellular and GPS modems to process data from the GPS satellite system and VCU. The VIU communicates with the rest of the vehicle over the class 2 serial data bus. Power moding for the VIU is accomplished over the class 2 serial data bus on some vehicles on the ignition 1 voltage circuit on others. The VIU also has the capability of commanding the horn, door unlock and exterior lamps using class 2 messages. For vehicles without this capability, the VIU uses specific, discrete circuits for commanding these features. When an OnStar® key press is made, a class 2 message is sent to the audio system to mute all radio functions and transmit OnStar® originated audio. On vehicles that do not use class 2 to communication with the audio system the VIU uses the entertainment and comfort (E & C) serial data circuit. After the audio system is muted, the OnStar® audio is transmitted to the vehicle audio system on the remote audio right signal circuit, the remote audio left signal circuit, and remote audio output (-).
Vehicle Communication Unit (VCU)
The Vehicle Communication Unit (VCU) is a 3 watt cellular transceiver that connects the OnStar® system to the cellular carrier's communication system. This module handles all cellular operations, sending and receiving all communications over the cellular antenna and cellular antenna coax. Power and ground for the VCU is provided by the VIU on the battery positive voltage and ground circuits. The VIU also supplies ignition voltage to the VCU over the ignition 1 voltage circuit. The VCU communicates with the VIU by using the OnStar® serial data (-) circuit, OnStar® serial data (+) circuit and the OnStar® serial data return circuit. The callers voice is carried to the VCU using the microphone signal circuit and the drain wire circuit. The audio signal is carried from the VCU to the VIU on the audio return signal circuit and the audio low reference circuit.
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, 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 VIU by means of either a cellular microphone low reference circuit or a drain wire.
Cellular and GPS Antennas
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 Unit. The GPS or, 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 key press 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 VIU 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 VIU and VCU are a set of unique numbers that identify the OnStar® customer and the specific vehicle the modules reside in. These numbers, the Station Identification Number (STID) and the Electronic Serial Number (ESN) are transmitted over the cellular network when an OnStar® key press is made and are essential for proper identification and connection to the OnStar® Call Center. In the event the VIU or VCU requires replacement, the OnStar® Reconfiguration procedure must be performed. This procedure allows for the new STID and ESN within the replacement modules to overwrite the old numbers and update customer and vehicle information at the OnStar® Call Center. The Reconfiguration process is explained within the VIU and VCU module replacement procedures.
Hands Free Cellular Phone
The hands free cellular phone is an additional feature to the OnStar® system. During a hands free call the microphone and audio system work the same way as a normal 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 is a specific command 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.
All the voice activated commands are interpreted by the VIU. A 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 you can say "HELP" and the 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, place a call to the OnStar® Call Center to verify proper operation of the microphone. Here 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.
