Cellular Communication System: Other Chevrolet Tahoe II

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS .

OnStar Always On

OnStar Always On

OnStar One or More Buttons Inoperative

OnStar One or More Buttons Inoperative

OnStar Call Center Unable to Configure OnStar (R) System

OnStar Call Center Unable to Configure OnStar (R) System

Microphone Inoperative - Caller Cannot Be Heard

Microphone Inoperative - Caller Cannot Be Heard

Voice Recognition Inoperative

Voice Recognition Inoperative

No (or Noisy) OnStar Audio

No (or Noisy) OnStar Audio

OnStar® Module Reprogramming

Vehicle Interface Unit (VIU)

1. Record the 10 digit Station I.D. (STID) number from the label on the new module.
2. Install the new VIU.
3. After replacement, press and hold the white "Dot" button until the OnStar status LED turns from green, to red, and then back to green.
4. Install a scan tool. Use the I.D. Information menu to access the new STID.
5. Move the vehicle to an open area that is away from tall buildings, and with a clear view of unobstructed sky. Allow the vehicle to run for 10 minutes.
6. Press the blue OnStar button to connect to the OnStar Call Center. Tell the advisor that this vehicle has received a new VIU and ask them to perform the following: Add the new STID to update the customer's account. Activate the OnStar Personal Calling feature if it is available in the area. Perform a full reconfiguration on the vehicle.
7. The OnStar® Advisor will reconfigure the vehicle with you. Once the advisor completes the reconfiguration, you can end the call. Follow any additional instructions given by the Advisor.
8. The old VIU must be returned for core credit with the address label included in the original box. Failure to return core will result in a debit.

Vehicle Communication Unit (VCU)

1. Record the 11 digit Electronic Serial Number (ESN) number from the label on the new module.
2. Install the new VCU.
3. After replacement, press and hold the white "Dot" button until the OnStar status LED turns from green, to red, and then back to green.
4. Install a scan tool. Use the I.D. Information menu to access the new ESN.
5. Move the vehicle to an open area that is away from tall buildings, and with a clear view of unobstructed sky. Allow the vehicle to run for 10 minutes.
6. Press the blue OnStar button to connect to the OnStar Call Center. Tell the advisor that this vehicle has received a new VCU and ask them to perform the following: Add the new ESN to update the customer's account. Activate the OnStar Personal Calling feature if it is available in the area. Perform a full reconfiguration on the vehicle.
7. The OnStar® Advisor will reconfigure the vehicle with you. Once the advisor completes the reconfiguration, you can end the call. Follow any additional instructions given by the Advisor.
8. The old VCU must be returned for core credit with the address label included in the original box. Failure to return core will result in a debit.

Scheme 43

Scheme 44

1. Remove the headliner. Refer to «HEADLINER REPLACEMENT»(ref-176028-S13031405502005042900000) .
2. Remove the IP trim panel. Refer to «TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER»(ref-175346-S38271644542005042000000) .
3. Remove the driver's side door sill plate. Refer to «DOOR SILL PLATE REPLACEMENT - FRONT»(ref-176028-S33333145762005042900000) .
4. Remove the hinge pillar trim moldings. Refer to «TRIM PANEL REPLACEMENT - HINGE PILLAR»(ref-176028-S35051946482005042900000) .
5. Disconnect the cable connector from the antenna inner coupling (1).
6. Remove the cable clips (2) from the roof and pillar.
7. Remove the cable from the body harness conduit (1).
8. Remove the cable clips (2) from underneath the IP.
9. Disconnect the cable connector (3) from the VCU.
10. Attach a wire to the end of the cable connector (3) in order for the coaxial cable to be pulled from underneath the IP.
11. Remove the wire from the coaxial cable.
12. Remove the cable from the vehicle.

Scheme 45

1. Attach the wire to the new coaxial cable.
2. From the top of the IP pull the wire till the coaxial cable can be connected to the VCU.
3. Remove the wire from the cable.
4. Connect the cable (3) to the VCU.
5. Install the cable clips to underneath the IP.
6. Lay the cable in the body harness conduit (1).
7. Install the cable clips (2) to the roof and pillar.
8. Connect the cable connector to the antenna inner coupling (1).
9. Install the hinge pillar trim moldings. Refer to «TRIM PANEL REPLACEMENT - HINGE PILLAR»(ref-176028-S35051946482005042900000) .
10. Install the driver's side door sill plate. Refer to «DOOR SILL PLATE REPLACEMENT - FRONT»(ref-176028-S33333145762005042900000) .
11. Install the IP trim panel. Refer to «TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER»(ref-175346-S38271644542005042000000) .
12. Install the headliner. Refer to «HEADLINER REPLACEMENT»(ref-176028-S13031405502005042900000) .

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 VIU or VCIM by means of either a cellular microphone low reference circuit or a drain wire.

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 or 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® keypress 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 communicate 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 (-).

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.

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 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 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 Sleep Cycle

The OnStar® 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 VIU to perform remote functions (such as door unlock) as commanded over the air by the OnStar® Call Center (when requested by the customer) and continue to maintain an acceptable level of battery electrical drain.

The OnStar® system uses three states of readiness

1. High Power
2. Low Power
3. Sleep

The High power state is in effect whenever the ignition is in the "ON" or "RUN" position, and enables the OnStar® 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 one minute and allows incoming cellular calls to be received. After the one minute "window", the OnStar® system moves to the Sleep state. This state will not recognize or receive incoming cellular calls. At a predetermined time recorded within the VIU (up to nine minutes), the system re-enters the Low power state to listen for a call from the OnStar® Call Center for one minute. After this interval, the system will again return to the Sleep state for nine minutes. After these nine minutes, the system will again enter the Low state of power and listen for any incoming calls that the OnStar® Call Center may be sending. In the event a call is being sent, the OnStar® 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 one-minute interval, the system will go back into the sleep mode for another nine minutes. This process will continue for up to 48 hours, after which, the OnStar® 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® 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 GPS signal can be acquired, providing a reference for time. The OnStar® 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.

Deactivated OnStar® Accounts

In the event a customer has not renewed their OnStar® account after expiration or the account was never activated, OnStar® will make a discrete cellular call to the vehicle to deactivate the OnStar® system. Before taking this action, customers are notified that the OnStar® 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 from their vehicle

1. During an OnStar® Call Center button press, the customer will be connected to a dedicated sales team who can sell an OnStar® subscription and reactivate the vehicle. Depending on the type of OnStar® hardware in the vehicle, the customer may first hear a demonstration message stating there is no current OnStar® subscription for the vehicle, and directing the customer what to do to activate services.
2. During an Emergency button press, a demo message will be played indicating the service has been deactivated.
3. OnStar® Personal Calling (OPC) will not be available, as this feature requires the customer to have a current OnStar® 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® system is successfully deactivated, it will NOT attempt to connect to the OnStar® Call Center in the event of a collision or if the vehicle's front air bags deploy for any other reason.

Certain vehicles that have never had an active OnStar® account, that have been deactivated, may be unable to establish a connection with the OnStar® 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® subscriber.

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® keypress 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 each individual module replacement procedure, or the OnStar® Reconfiguration Procedure found in the Cellular Communication diagnostic information and procedures section.

OnStar® Personal Calling

The hand free, OnStar® Personal Calling (OPC) cellular phone feature is an additional option to the OnStar® system. This feature is already embedded within the VIU, however, it must be activated by an OnStar® advisor. This is done most often during the initial OnStar® configuration, if the home location of the vehicle is in a geographic area where OnStar® Personal Calling is available. In the event this feature is not enabled, customers may connect to the OnStar® Call Center by pressing the blue OnStar® button, and asking an advisor if OPC is available in their area.

OPC Features

The following is an abbreviated list of features that may have an impact for the technician when servicing or diagnosing an OnStar® system. For a full list of OnStar® Personal Calling features, consult the owners guide provided to the customer with the OnStar® system.

Voice Feedback

The OPC system has the capability of responding to the user with either an automated voice response or with a tone or "beep". These two types of responses can be switched back and forth by pressing the answer/end call button, waiting for the system to respond "Ready" and speaking the phrase "voice feedback". The system will then respond, "voice feedback is now on/off".

OPC Security/System Lock

Customers have the capability to lock their OPC system by pressing the answer/end call button, speaking "security" and entering a four-digit code. Once this process is complete, the user must enter the code before OnStar® Personal Calling is available. In the event the customer cannot remember their code and is unable to use their system, they can press the blue OnStar button and speak to an advisor to unlock the system by means of a discrete cellular call to the vehicle.

Nametags

Customers have the ability to store telephone numbers within the module, referenced by a "nametag" for the convenience of frequently dialed numbers. This process is initiated by pressing the answer/end call button, waiting for the system response, then speaking the response "store". The system will respond with "number please" at which time the user should enter the number desired to be stored. Once complete, saying the word "store" again lets the system know you are finished entering the number. At this time, the system will elicit the user to assign a "nametag" to that number. From this point forward, the user can dial this number by initiating the OPC feature, speaking the word "call", and repeating the nametag assigned. To delete a nametag, the user should initiate OPC, say "delete" then speak the nametag to be removed. In the event a nametag cannot be deleted in spite of repeated attempts from several speakers, the VCIM or VIU will require replacement.