Chevrolet Silverado / GMC Sierra. Service manual — part 2233

Ignition ON, press the OnStar® Call buttons one at the time. Verify that all of the OnStar®
buttons operate normally.

If some OnStar® buttons are inoperative but not all, replace the inside rearview mirror.

If none of the OnStar® buttons operate, refer to circuit/system testing.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.

2. Ignition ON, test for 9.8-10.2 volts between the keypad supply voltage circuit terminal 12

and ground.

If less than the specified range, test the supply voltage circuit for a short to ground or
open/high resistance. If the circuit tests normal, replace the CIM.

If greater than the specified range, test the supply voltage circuit for a short to voltage.
If the circuit tests normal, replace the CIM.

3. Test for 0 volt between the keypad signal circuit terminal 11 and ground.

If greater than the specified range, test the keypad signal circuit for a short to voltage.
If the circuit tests normal, replace the CIM.

4. Test for 9.8-10.2 volts between the keypad supply voltage circuit terminal 12 and the

keypad signal circuit terminal 11.

If less than the specified range, test the keypad signal circuit for an open/high
resistance. If the circuit tests normal, replace the CIM.

5. Test for less than 5 ohms between the mirror ground circuit terminal 8 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

6. Ignition OFF, disconnect the CIM X1 connector. Test for infinite resistance between the

keypad signal circuit terminal 11 and ground.

If less than the specified range, test the keypad signal circuit for a short to ground.

7. If all circuits test normal, test or replace the button assembly.

Component Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.

2. Test for infinite resistance between the keypad supply voltage terminal 12 and the keypad

signal terminal 11.

IMPORTANT: Contact the OnStar® Call Center first before pressing the

emergency button in order to notify them of the test.

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If less than the specified range, replace the inside rearview mirror.

3. Test for 1.4k-1.6k ohms between the keypad supply voltage terminal 12 and the keypad

signal terminal 11 while pressing the black phone button.

If not within the specified range, replace the inside rearview mirror.

4. Test for 2.7k-3.3k ohms between the keypad supply voltage terminal 12 and the keypad

signal terminal 11 while pressing the blue On-Star® button.

If not within the specified range, replace the inside rearview mirror.

5. Test for 11.7k-14.3k ohms between the keypad supply voltage terminal 12 and the keypad

signal terminal 11 while pressing the red emergency button.

If not within the specified range, replace the inside rearview mirror.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Inside Rearview Mirror Replacement

Control Module References for CIM replacement, setup, and programming

ONSTAR RECONFIGURATION (WITH TIS 2 WEB GEN 4 AND LATER)

IMPORTANT:

The vehicle communication interface module (VCIM) has a
specific set of unique numbers that tie the module to a
specific vehicle. These numbers, the 10-digit station
identification (STID) and 11-digit electronic serial number
(ESN), are used by OnStar® and the cellular network to
identify the specific vehicle. Because these numbers are
exclusive to the vehicle identification number of the vehicle,
these parts should NOT be exchanged with those of another
vehicle. After replacing the VCIM, it is essential to
reconfigure the OnStar® system. Failure to reconfigure the
system will result in an additional customer visit for repair.
DO NOT press and hold the white dot button on the keypad as
it will not reset this version of the OnStar® system and may
result in a DTC to be set, a red LED and limited or incomplete
OnStar® services. Use of the TIS 2 Web SPS application and
the Tech 2 are required in order to perform the VCIM
configuration and setup procedure for this vehicle. The
configuration and set-up procedure is now a two step

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1. Connect the Tech 2 to the vehicle.

2. Connect the Techline Information System (TIS) terminal to the Tech 2.

3. Select the OnStar® Activation programming option using the service programming system

(SPS).

4. Upon completion of the OnStar® Activation programming event, disconnect the TIS

terminal from the Tech 2 and perform the VCIM/OnStar Set-up Procedure using the Tech 2.
The set up procedure is located under the special function menu option.

5. The default language for the new VCIM is English. Changing the language capability to

French or Spanish is supported by service programming system (SPS) and by Tech 2 special
functions. Changing the language capability is also dependant on the generation of the
replacement OnStar module.

Inform the customer that it may take up to 24 hours for the OnStar® service to become fully
activated after performing the TIS 2 Web and Tech 2 setup procedures.

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 is depressed during an OPC call, the vehicle
communication interface module (VCIM) receives the message on the class 2 or GMLAN serial
data bus from either the radio, driver information module, or 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

process which enables an automated activation by the
OnStar Center, without a button press by the technician to
the center.

It may take up to 24 hours for the OnStar® service to become
fully activated after performing the TIS 2 Web and Tech 2
setup procedures. Perform the OnStar® Activation procedure
only once. Repeat attempts at performing the procedure may
result in a delay of the activation process.

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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 (DIM), or BCM. In the event the
OnStar® steering wheel control functions are inoperative, technicians should refer to Steering
Wheel Controls Inoperative , to begin diagnosis of the steering wheel control concern.

ONSTAR SYMPTOM DIAGNOSIS

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The vehicle communication interface module (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 the 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 2 modems, one to process
global positioning system (GPS) data, and the other for 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 VCIM communicates with the rest of the
vehicle over the class 2 or GMLAN serial data bus, depending upon the serial data architecture of
the vehicle. The ignition state is determined by the VCIM through class 2 or GMLAN messaging.
The module also has the capability of commanding the horn, initiating door lock/unlock and
operating the exterior lamps using the serial data circuits. When an OnStar® keypress is made, a
serial data message is sent to the audio system to mute all radio functions and transmit OnStar®
originated audio. After the audio system is muted, the OnStar® signals are transmitted to the
audio system on the left audio signal circuit, and the audio common signal circuit. The cellular
modem connects the OnStar® system to the cellular carriers 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.

Diagnostic Aids

The customer concern may have been due to a lack of cellular service in a given area or a
failure in the National Cellular Network infrastructure that has since been corrected.

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