Cellular Communication System: Diagnosis Chevrolet Silverado 3500

Diagnostic Starting Point - Cellular Communication

Begin the system diagnosis with Diagnostic System Check - Cellular Communication . The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. 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.

Scan Tool Data List (Gen 5)

Scan Tool Data List (Gen 5)

Scan Tool Data List (Gen 6)

Scan Tool Data List (Gen 6)

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

The vehicle communication interface module (VCIM) detects that the cellular microphone is connected through the cellular microphone signal circuit and the cellular microphone low reference circuit.

Conditions for Running the DTC

1. The ignition must be in the RUN or ACC position.
2. The system voltage is at least 9.5 volts and no more than 15.5 volts.
3. All the above conditions are present for greater than 10 seconds.

Conditions for Setting the DTC

1. The VCIM detects an open in the cellular microphone signal circuit or drain wire circuit.
2. The VCIM detects a short to voltage in the cellular microphone signal circuit.
3. The above conditions are present for greater than 10 seconds.

Action Taken When the DTC Sets

1. The VCIM will not receive any signal from the microphone.
2. Calls can be placed but the caller cannot be heard.
3. The OnStar® status LED turns RED.

Conditions for Clearing the DTC

1. The VCIM detects the microphone connected for 5 consecutive 100 millisecond cycles.
2. A history DTC clears after 50 malfunction free ignition cycles.
3. The VCIM receives the clear DTC command from the scan tool.

The cellular portion of the cellular and navigation antenna is connected to the vehicle communication interface module (VCIM) with a RG-174 coax cable. The VCIM polls the data from the antenna once every second.

1. The ignition must be in the RUN or ACC position.
2. The system voltage is at least 9.5 volts and no more than 15.5 volts.
3. All the above conditions are present for greater than 1 second.

1. The VCIM does not detect the presence of the cellular antenna
2. All the above conditions are present for greater than 1 second.

1. The OnStar® status LED turns RED.
2. The vehicle is unable to connect to the OnStar® Call Center.

1. The VCIM detects the presence of the cellular and navigation antenna.
2. A history DTC clears after 50 malfunction free ignition cycles.
3. The VCIM receives the clear DTC command from the scan tool.

The OnStar® button assembly consists of three buttons, Call/Answer, OnStar® Call Center and OnStar® Emergency. Ten volts is supplied to the button assembly on the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resister allowing a specific voltage to be returned to the vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.

1. The ignition must be in the RUN or ACC position.
2. The system voltage is at least 9.5 volts and no more than 15.5 volts.
3. All the above conditions are present for greater than 300 ms.

1. The keypad signal circuit voltage to the VCIM is less than 2.8 volts or more than 3.2 volts.
2. The above conditions are present for greater than 300 ms.

1. The VCIM will ignore all inputs from the OnStar® button assembly.
2. No calls can be placed.
3. The OnStar® status LED turns RED.

1. The keypad signal circuit voltage is between 2.8 volts and 3.2 volts.
2. A history DTC clears after 50 malfunction free ignition cycles.
3. The VCIM receives the clear DTC command from the scan tool.

The OnStar® button assembly consists of three buttons, Call/Answer, OnStar® Call Center and OnStar® Emergency. Ten volts is supplied to the button assembly on the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resister allowing a specific voltage to be returned to the vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the VCIM is able to identify which button has been pressed.

1. The ignition must be in the RUN or ACC position.
2. The system voltage is at least 9.5 volts and no more than 15.5 volts.
3. All the above conditions are present for greater than 15 seconds.

1. A button is pressed or stuck for more than 15 seconds.
2. The above conditions are present for greater than 15 seconds.

1. The VCIM will ignore all inputs from the OnStar® button assembly.
2. No calls can be placed.
3. The OnStar® status LED turns RED.

1. The button will be declared unstuck after a 50 ms normal cycle.
2. A history DTC clears after 50 malfunction free ignition cycles.
3. The VCIM receives the clear DTC command from the scan tool.

The navigation portion of the cellular and navigation antenna is connected to the vehicle communication interface module (VCIM) with a RG-174 coax cable. The VCIM polls the data from the antenna once every second.

1. The ignition must be in the RUN or ACC position.
2. The system voltage is at least 9.5 volts and no more than 15.5 volts.
3. All the above conditions are present for greater than 1 second.

1. The VCIM does not detect a navigation signal.
2. All the above conditions are present for greater than 1 second.

1. The OnStar® status LED turns RED.
2. The OnStar® Call Center cannot locate the vehicle.

1. The VCIM detects the presence of the cellular and navigation antenna.
2. A history DTC clears after 50 malfunction free ignition cycles.
3. The VCIM receives the clear DTC command from the scan tool.

DTC B2483 or B2484

This DTC indicates an internal fault and is set within the vehicle communication interface module (VCIM). No external circuits are involved.

The microprocessor runs the program to detect an internal fault during module power up and every 10 seconds thereafter until the module re-enters the sleep mode.

The VCIM detects an internal communication malfunction.

Action Taken When DTC Sets

1. The OnStar® status LED turns RED.
2. The vehicle is unable to connect to the OnStar® Call Center.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears after 50 malfunction free ignition cycles.

Diagnostic Aids

1. The diagnostic procedure used for DTC U1500 in OnStar® systems with single module generations of OnStar® differ greatly from previous generations with 2 modules. While these older generations denoted a failure of the 3-wire bus between the modules by setting a U1500, single module OnStar® systems use this DTC to denote an internal module failure. The determination of whether a one or 2-module generation of OnStar® is used should be confirmed. Refer to «OnStar Description and Operation»(ref-184110-S08882044602005082200000) .
2. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the VCIM.
3. If this DTC is retrieved as both a current and history DTC, replace the VCIM.

DTC U1500

1. 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.
2. If the prompt OnStar request ended is heard without pressing the white dot button at the end of an OnStar® keypress, the OnStar® system at one time has made a successful cellular connection, but was unable to complete the call. If repeated calls are placed with this result, contact the General Motors Technical Assistance Center.
3. Inaccurate or aged global positioning system (GPS) position may have been due to the temporary loss of GPS signal reception by the vehicle in instances such as driving through tunnels or parking structures which restrict the navigation antenna from a clear view of the satellites in the sky.

OnStar Symptom Diagnosis

Symptoms - Cellular Communication

1. Perform the «Diagnostic System Check - Cellular Communication»(ref-184110-S02198817772005082200000) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control module can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «OnStar Description and Operation»(ref-184110-S08882044602005082200000) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the system. Refer to «Checking Aftermarket Accessories»(ref-184114-S31353837752005082200000) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «OnStar One or More Buttons Inoperative»(ref-184110-S21667186082005082200000)
2. «Unable to Contact OnStar Call Center»(ref-184110-S06966822882005082200000)
3. «OnStar Button LED Inoperative»(ref-184110-S02332188572005082200000)
4. «No (or Noisy) OnStar Audio»(ref-184110-S31273789462005082200000)
5. «Microphone Inoperative - Caller Cannot Be Heard»(ref-184110-S30028795222005082200000)
6. «Voice Recognition Inoperative»(ref-184110-S40012147922005082200000)
7. «OnStar Steering Wheel Control Functions Inoperative»(ref-184110-S28567957022005082200000)
8. «Global Positioning System (GPS) Data Not Current or Inaccurate»(ref-184110-S01335054432005082200000)
9. «OnStar Call Center Remote Function Requests Inoperative»(ref-184110-S19319475962005082200000)

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.

OnStar Call Center Remote Function Requests Inoperative

1. The customer concern may have been due to a lack of cellular service in a given area. A failure in the National Cellular Network infrastructure at the time of the customers failed connection that has since been repaired may also have been the cause.
2. If an OnStar® Emergency call is able to successfully connect the vehicle to the OnStar® Call Center when an OnStar® Call Center button press is not, there may be a failure in the ability of the OnStar® system in the vehicle to be recognized by the local cellular carrier.
3. If the prompt "OnStar® request ended" is heard without depressing the white "Dot" button at the end of the an OnStar® keypress, the OnStar® system at one time has made a successful cellular connection but was unable to complete the call. If repeated calls are placed with this result, contact the General Motors Technical Assistance Center.

Unable to Contact OnStar Call Center

1. The GPS Signal title on the scan tool will display a Yes or No dependent upon whether or not the module sees an increment of the seconds transmitted by global positioning system (GPS) signals to the vehicle communication interface module. Upon entering this screen, the GPS Signal title will automatically display Yes, regardless of the presence of time increment, for at least 2 seconds, while the algorithm in the scan tool determines the status of the clock. If increment is found, Yes is continually displayed. If the clock remains static, No is displayed. The scan tool looks for increment every second, regardless of current display.
2. Inaccurate or aged GPS position concerns made by a customer which are no longer present may have been due to the temporary loss of GPS signal reception by the vehicle. Conditions such as driving through tunnels or parking structures while making an OnStar® keypress will restrict the navigation antenna from a clear view of the satellites in the sky and may have caused this temporary data loss.

Global Positioning System (GPS) Data Not Current or Inaccurate

OnStar® Cellular, GPS, and Diagnostic Limitations

The proper operation of the OnStar® 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 global positioning system (GPS) system.

The cellular operation of the OnStar® system may be inhibited by factors such as the user's range from an analog (Generation 5) or digital (Generation 6) cellular tower, the state of the cellular carriers' equipment, and the location where the call is placed. Making an OnStar® keypress 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® Call Center. The OnStar® system may also experience connection issues if the identification numbers for the module, station identification number (STID) and electronic serial number (ESN), are not recognized by the cellular carriers local signal receiving towers. OnStar® cellular connection issues such as these require the assistance of the General Motors Technical Assistance Center OnStar® Group, which coordinates with cellular carriers to resolve connection issues.

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® 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 (Generation 5) or digital (Generation 6) 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.