Part 1
OnStar(R) Description and OperationThis OnStar(R) digital system consists of the following components:
^ Vehicle Communication Interface Module (VCIM)
^ OnStar(R) button assembly
^ Microphone
^ Cellular antenna
^ Navigation antenna
Note
This system also interfaces with the factory installed vehicle audio system.
Vehicle Communication Interface Module (VCIM)
The vehicle communication interface module (VCIM) is a cellular device that allows the user to communicate data and voice signals over the national cellular network. Power is provided by a dedicated, fused B+ circuit. Ground is provided through the vehicle wiring harness attached to the module. The ignition state is determined by the VCIM through serial data messaging.
Dedicated circuits are used to connect the VCIM to a microphone, the button assembly, and to command the status LED. The VCIM communicates with the rest of the vehicle modules using the serial data bus.
The module houses 2 technology systems, one to process GPS data, and another for cellular information. The cellular system 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. GPS satellites orbiting earth are constantly transmitting signals of their current location. The OnStar(R) system uses the GPS signals to provide location on demand.
The module also has the capability of activating the horn, initiating door lock/unlock, or activating the exterior lamps using the serial data circuits. These functions can be commanded by the OnStar(R) Call Center per: a customer request.
OnStar(R) Button Assembly
The OnStar(R) button assembly may be part of the rearview mirror, or a separate, stand alone unit. The button assembly is comprised of 3 buttons and a status LED. The buttons are defined as follows:
^ The answer/end call button, which is black with a white phone icon, allows the user to answer and end calls or initiate speech recognition.
^ The blue OnStar(R) call center button, which displays the OnStar(R) logo, allows the user to connect to the OnStar(R) call center.
^ The emergency button, which displays a white cross with a red background, sends a high priority emergency call to the OnStar(R) call center when pressed.
The VCIM supplies 10 volts to the OnStar(R) button assembly on the keypad supply voltage circuit. When pressed, each button completes a circuit across a resistor allowing a specific voltage to be returned to the 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 with the button assembly. 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.
If the LED does not illuminate, this may indicate that the customers OnStar(R) subscription is not active or has expired. Push the blue OnStar button to connect to an advisor who can then verify the account status.
Each LED is controlled by the VCIM over dedicated LED signal circuits. Ground for the LED is provided by the wiring harness attached to the button assembly.
OnStar(R) Microphone
The OnStar(R), or cellular microphone, can be a part of the rearview mirror assembly, or on some vehicle lines, a separate, stand alone unit.
In either case, the VCIM supplies approximately 10 volts to the microphone on the cellular microphone signal circuit, and voice data from the user is sent back to the VCIM over the same circuit. A cellular microphone low reference circuit or a drain wire provides a ground for the microphone.
Cellular and GPS Antennas
The vehicle will be equipped with one of the following types of antennas:
^ Separate, stand-alone cellular and navigation (GPS) antennas.
^ A combination cellular and navigation (GPS) antenna, which brings the functions of both into a single part.
^ A cellular, GPS, and digital radio receiver (DRR) antenna, which also incorporates the functionality of the DRR satellite antenna (XM).
The cellular antenna is the component that allows the OnStar(R) system to send and receive data using electromagnetic waves by means of cellular technology. The antenna is connected at the base to a coax cable that plugs directly into the VCIM.
The GPS antenna is used to collect the signals of the orbiting GPS satellites. Within the antenna is housed a low noise amplifier that allows for a more broad and precise reception of this data. The antenna is connected at the base to a coax cable that plugs directly into the VCIM. The cable also provides a path for DC current for powering the antenna.
The OnStar(R) Call Center also has the capability of communicating with the vehicle during an OnStar(R) call 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, for as long as the module power is not removed. Actual GPS location may take up to 10 minutes to register in the event of a loss of power.
Audio System Interface
When the OnStar(R) requires audio output, a serial data message is sent to the audio system to mute all radio functions and transmit OnStar(R) originated audio. The OnStar(R) audio is transmitted to the vehicle audio system by a dedicated signal circuit and a low reference circuit.
The audio system will mute and an audible ring will be heard though the speakers if the vehicle receives a call with the radio ON.
On some vehicles, the HVAC blower speed may be reduced when the OnStar(R) system is active to aid in reducing interior noise. When the system is no longer active, the blower speed will return to its previous setting.
OnStar(R) Steering Wheel Controls
Some vehicles may have a button on the steering wheel, that when pushed can engage the OnStar(R) system. The button may be a symbol of a face with sound waves, or may say MUTE, or be a symbol of a radio speaker with a slash through it.
By engaging the OnStar(R) system with this feature, the user can interact with the system by use of voice commands. A complete list of these commands is supplied in the information provided to the customer. If the information is not available for reference, at any command prompt, the user can say "HELP" and the VCIM will return an audible list of available commands.
The steering wheel controls consist of multiple momentary contact switches and a resistor network. 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. This produces a specific voltage value unique to the switch selected, to be interpreted by the radio or the body control module (BCM).
OnStar(R) Power Moding (DRX or Sleep Cycle)
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 and retained accessory power (RAP) mode has ended.
A green status LED on the OnStar(R) keypad normally indicates an active OnStar(R) account. The OnStar(R) system will stay powered up after ignition off for an extended time in order to allow for remote services like door unlock, horn honk, light flash, etcetera to take place as requested by the customer. Power cycle (also referred to as DRX) times vary depending on the generation of the OnStar(R) system. Technicians may identify the OnStar(R) system generation by using a Tech 2 and following this menu path: (Body>VCIM>Module ID Information>Module Information 2) or by accessing www.onstarenrollment.com
All Generation 6 digital systems are powered up continuously for 48 hours from ignition OFF. After 48 hours, the Generation 6 systems will enter a 9 minute OFF, 1 minute ON power cycle for an additional 72 hours. At the beginning and end of the 1 minute ON stage, you may or may not experience a short spike of current at the beginning and at the end. This allows for calls from OnStar to be received by the system. After 120 hours from ignition OFF, these systems will then completely power OFF.
OnStar(R) Module Expected Current Draw
The expected current draw of the OnStar(R) module in various ignition modes are as follows:
^ Ignition ON ‐ 240 to 400 mA
^ Ignition OFF ‐ 3 to 20 mA for 48 hours
^ Ignition OFF ‐ 0.2 to 0.8 mA after 48 hours (120 hours on specified vehicle communication platforms (VCPs)).
Note
During extended voltage testing for battery parasitic draw, it is possible to observe a voltage spike caused by the following:
^ A cellular registration call that was triggered by the local cellular system.
^ The OnStar(R) system has set a monthly trigger for a vehicle data upload call for the OnStar(R) Vehicle Diagnostic E‐mail upload.
OnStar(R) System States of Readiness
The OnStar(R) system will use the following 4 states of readiness, depending upon the type of cellular market the vehicle is in when the ignition is turned OFF.
^ High power
^ Low power
^ Sleep
^ Digital standby
The high power state is in effect whenever the ignition is in the ON or RUN position, retained accessory power (RAP) is enabled, and/or the OnStar(R) system is sending or receiving calls or when the system is performing a remote function.
The low power state is in effect when the OnStar(R) system is idle with the ignition in the ON or RUN position, or with RAP enabled.
The sleep state is entered after the vehicle has been shut OFF and the RAP has timed out. At a predetermined time recorded within the VCIM, 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. If a call is sent during the 1 minute interval, the OnStar(R) system will receive the call and immediately go into the high power mode to perform any requested functions. If a call is not 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 turn OFF until the ignition is turned to the ON or RUN position.
The digital standby power state is entered after the vehicle has been shut off and the RAP has timed out while in a digital cellular area. When in digital standby mode, the OnStar(R) module is able to perform all remote functions as commanded by an OnStar(R) advisor at any time, for a continuous 48 hours. After 48 hours, the OnStar(R) module will go into sleep mode until a wake up signal from the vehicle is seen by the CIM. If the OnStar module loses the digital cellular signal it will revert to analog mode and follow the standard sleep state (9 minutes OFF, 1 minute standby) based on the time of the GPS signals, this will continue until a digital cellular signal is again received.
If the OnStar(R) system loses battery power while the system is in a standby or sleep mode, the system will remain OFF until battery power is restored and the ignition is turned to the ON or RUN position.
Deactivated OnStar(R) Accounts
In the event that a customer has not upgraded their vehicle to a digital system, the account has been deactivated. The customers have been previously notified of the steps required to upgrade their vehicles. After the OnStar(R) account has been deactivated, customers will experience the following:
^ The OnStar(R) status LED will not illuminate
^ The OnStar(R) system will NOT attempt to connect to the OnStar(R) Call Center in the event of a collision or if the vehicle's front air bags deploy for any other reason.
^ An emergency button press will result in a demo message being played, indicating the service has been deactivated and needs to be upgraded.
^ An OnStar(R) Call Center button press WILL NOT connect the vehicle with OnStar(R). The vehicle must be upgraded to reactivate the account. The customer will hear a demo message stating that there is not a current OnStar(R) subscription for the vehicle. The message will also instruct the customer how to upgrade and reactivate services.
^ 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 will result in cellular connection failure messages and the inability to connect to the number dialed.
Note
For deactivated vehicles, a no connect response should be considered normal system operation. Further diagnosis and subsequent repair is only necessary should the customer elect to become an active OnStar(R) subscriber and upgrade the account subscription.
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 GPS.
The cellular operation of the OnStar(R) system may be inhibited by factors such as the users range from a digital cellular tower, the state of the cellular carrier's equipment, and the location where the call is placed. Making an OnStar(R) key press in areas that lack sufficient cellular coverage or have a temporary equipment failure will result in either the inability of a call to complete with a data transfer or the complete inability to connect to the OnStar(R) Call Center. The OnStar(R) system may also experience connection issues if the identification numbers for the module, station identification number (STID), electronic serial number (ESN) or manufacturers electronic ID (MEID), are not recognized by the cellular carriers local signal receiving towers.
The satellites that orbit earth providing the OnStar system with GPS data have almost no failures associated with them. In the event of a no GPS concern, the failure will likely lie with the inability of the system to gain GPS signals because of its location, i.e. in a parking structure, hardware failure, or being mistaken with an OnStar(R) call which has reached the Call Center without vehicle data.
During diagnostic testing of the OnStar(R) 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 digital cellular calls have been successfully placed. These areas can be found by successfully making an OnStar(R) keypress in a known good OnStar(R) equipped vehicle and confirming success with the OnStar(R) Call Center advisor. Such places can be used as a permanent reference for future OnStar(R) testing.
Mobile Identification Number and Mobile Directory Number
The vehicle communication interface module (VCIM) utilizes 2 numbers for cellular device identification, call routing and connection.
They are:
^ A mobile identification number (MIN)
^ A mobile directory number (MDN)
Note
The MIN represents the number used by the cellular carrier for call routing purposes. The MDN represents the number dialed to reach the cellular device.
Diagnostic Information
Symptoms - Cellular Communication
The following steps must be completed before using the symptom table.
1. Perform the Diagnostic System Check - Vehicle, before using the Symptom Tables in order to verify that the following are true:
^ There are no DTCs set.
^ The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to Radio/Audio System Description and Operation in SI.
Diagnostic Starting Point - Displays and Gages
Begin the displays and gages system diagnosis with Diagnostic System Check - Vehicle or the audible warning system diagnosis with Diagnostic System Check - Vehicle. The Diagnostic System Check will provide the following information:
^ The identification of the control modules which command the system
^ The ability of the control modules to communicate through the serial data circuit
^ The identification of any stored diagnostic trouble codes (DTCs) and their status
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.
Visual/Physical Inspection
Perform the following visual inspections;
^ Inspect for aftermarket devices which could affect the operation of the Radio/Audio System. Refer to Checking Aftermarket Accessories in SI.
^ Inspect the easily accessible and visible system components for obvious damage or conditions which could cause the symptom.
Intermittent Conditions
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in SI.
Symptom List
Diagnostic Trouble Codes
DTC U1000 and U1255
Circuit/System Description
Modules connected to the Class 2 serial data circuit monitor for serial data communications during normal vehicle operation.
Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 or U1255 DTC is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once.
The Class 2 serial data communications circuit on this vehicle are in a hybrid ring and star configuration. Each module on the ring has 2 serial data circuits connected to it, except the following modules which have only 1 serial data circuit connected them:
^ Audio amplifier
^ Driver door module (DDM)
^ Driver door switch assembly (DDSA)
^ Front passenger door module (FPDM)
^ Left rear door module (LRDM)
^ Memory seat module (MSM)
^ Radio antenna module (listed as remote function actuation in scan tool display)
^ Rear integration module (RIM)
^ Right rear door module (RRDM)
^ Theft deterrent module (TDM)
^ TV antenna module
^ Vehicle communication interface module (VCIM)
The star has 4 splice packs:
^ SP200 located in the left side of the instrument panel, near the steering column , taped to the instrument panel harness
^ SP201 located in the center of the instrument panel, near the radio
^ SP300 located in the left side middle of the passenger compartment, taped to the body harness, near the carpet seam
^ SP303 located in the right rear of the passenger compartment, taped to the body harness, approximately 24 cm (9.5 in) from the fuse block - right rear. Refer to Data Communication Schematics in SI.
The following modules, components, and splice packs are connected to the ring portion of the class 2 serial data circuit:
^ Dash integration module (DIM)
^ Electronic brake control module (EBCM)
^ Engine control module (ECM)
^ Inflatable restraint sensing and diagnostic module (SDM)
^ Instrument panel cluster (IPC)
^ HVAC control module
^ Radio
^ Rear integration module (RIM)
^ Vehicle communication interface module (VCIM)
OR
^ Communication interface module (CIM)
^ SP200
^ SP201
^ SP300
^ SP303
The following modules, components, and splice pack are connected to the star portion of the class 2 serial data circuit:
^ SP300
^ Audio amplifier
^ Driver door module (DDM)
^ Driver door switch assembly (DDSA)
^ Memory seat module (MSM)
^ Left rear door module (LRDM)
AND
^ SP303
^ Antenna module
^ Front passenger door module (FPDM)
^ Rear integration module (RIM)
^ Right rear door module (RRDM)
^ Theft deterrent module (TDM)
^ Vehicle communication interface module (VCIM). Refer to Data Communication Schematics and Data Link Communications Description and Operation in SI.