Chevrolet Silverado / GMC Sierra. Service manual — part 2249

hardware failure, or being mistaken with an OnStar® call which has reached the Call Center
without vehicle data.

During diagnostic testing of the OnStar® 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 analog or digital cellular calls have been successfully placed. These areas can be found by
successfully making an OnStar® keypress in a known good OnStar® equipped vehicle and
confirming success with the OnStar® Call Center advisor. Such places can be used as a
permanent reference for future OnStar® testing.

OnStar® Personal Calling

The hands free, OnStar® personal calling (OPC) cellular phone feature is an additional option to
the OnStar® system. This feature is already embedded within the vehicle communication
interface module (VCIM), 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. Users of the OnStar® system can
verify the system has been configured for OnStar® Personal Calling by pressing the answer/end
call button, waiting for the system to respond "OnStar® Ready" then speaking the word "dial." If
the system responds with a failure message, the system has not been configured for OPC. All other
responses confirm that OPC has been enabled.

Operation of the Hands Free Cellular Phone

Onstar® personal calling (OPC) operates similar to most hand held cellular phones in that the
availability for its usage is based on minutes or units. The customer must have a current OnStar®
subscription, as this feature cannot be utilized without it. To use OPC, the customer must also
purchase units as outlined in the owners guide provided with the OnStar® system. When the
customer purchases minutes, an OnStar® advisor loads these minutes into the vehicle
communication interface module (VCIM) over the airwaves at the time of the request, or through
a discrete cellular call to the vehicle at a later time. Once loaded into the module, the units may
be used for non-international, outbound cellular phone calls, and connection with the OnStar®
virtual advisor. Units begin to deplete, 1 unit is equal to 1 minute, as the customer makes
outbound phone calls, answers inbound phone calls, or while connected to the OnStar® virtual
advisor. In addition, units also have an expiration date, depending upon the type of units
purchased. This date is established when the download is performed, and any remaining units
expire when the date within the VCIM, global positioning system (GPS) satellites, has passed. At
any time, the user can press the answer/end call button, say "Units" and verify the number of units
remaining.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Cellular, Entertainment, and Navigation - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

During a hands free call, the microphone and audio system operate the same way as a standard
OnStar® call. When the answer/end call button is pressed, the audio system will mute; the
OnStar® system will then return the prompt "OnStar® Ready." At this point there are specific
commands 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.

The VCIM interprets all of the voice-activated commands. A complete 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 the caller can say "HELP" and the VCIM will return an
audible list of available commands. If the customer concern is not being understood or not being
heard by the OnStar® system, the user should place a call to the OnStar® call center to verify
proper operation of the microphone. Following this description 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.

OnStar® Steering Wheel Controls

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 module (VCIM) receives the message on the serial data bus from either the radio,
the driver information module, or the body control module (BCM). 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, driver information module, or BCM.

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 (OPC)
features, consult the owner's guide provided to the customer with the OnStar® system.

Voice Feedback

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Cellular, Entertainment, and Navigation - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

The OnStar® personal calling (OPC) system has the capability of responding to the user with
either an automated voice response or with a tone or beep. These 2 types of responses can be
switched back and forth by pressing the answer/end call button, waiting for the system to respond
"OnStar® 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 OnStar® personal calling (OPC) system by pressing
the answer/end call button, speaking "security" and entering a 4-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 OnStar®
personal calling (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 OnStar® module will require replacement.

Mobile Identification Number and Mobile Directory Number

The vehicle communication interface module (VCIM) utilizes 2 numbers for cellular device
identification, call routing and connection, a mobile identification number (MIN) and a mobile
directory number (MDN). The MIN represents the number used by the cellular carrier for call
routing purposes while the MDN represents the number dialed to reach the cellular device.
Although technicians have the capability to change these numbers by means of the scan tool, this
should ONLY be done at the direction of and with explicit instruction from General Motors
Technical Assistance Center (GM TAC).

Placing a Call

To Dial a Number

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Cellular, Entertainment, and Navigation - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

After 3 unsuccessful tries, or if you simply like it better, you can use the "Digit Dial" command to
input digits one at a time. Digit Dial is set up to dial phone numbers like previous OnStar®
Personal Calling Systems.

To Dial a Number Using Digit Dial

To Place a Call Using a Stored Nametag

To Place a Call Using the "Redial" Command

Operation of the OnStar® Speech Recognition Systems

OnStar® users communicate with 2 speech recognition systems. Speech recognition allows the
user to speak to one computer in the vehicle, and one reached over a phone line. The computer
tries to understand the users command, and responds by speaking back, or by taking the
appropriate action, e.g. dialing the phone.

What You Do

What You Hear

Press the white dot button

"OnStar® Ready"

Say "Dial"

"Phone number to dial, please"

Say the entire phone number you wish to dial

with no pauses

OnStar® will repeat the number, then ask

"Yes or No"

Say "Yes" if the phone number was correct,

or "No" to try again

"Dialing," and your call will be connected

What You Do

What You Hear

Press the white dot button

"OnStar® Ready"

Say "Digit Dial"

"First digit to dial, please"

Say the number to be dialed, one digit at a

time

OnStar® will confirm each digit by repeating

it back to you

When finished, say "Dial" again

"Dialing," and your call will be connected

What You Do

What You Hear

Press the white dot button

"OnStar® Ready"

Say "Call"

"Nametag, please"

Say (stored name)

"Calling"

What You Do

What You Hear

Press the white dot button

"OnStar® Ready"

Say "Redial"

"Redialing"

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Cellular, Entertainment, and Navigation - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado