Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

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 customer's failed connection that has since been repaired may also have been the cause.
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.
If the prompt "OnStar® request ended" is heard, without pressing the white dot button at the end of the 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 General Motors Technical Assistance Center.

Unable to Contact OnStar Call Center

Step	Action	Value	Yes	No
Schematic Reference: OnStar Schematics Connector End View Reference: Entertainment/Communication Connector End Views DEFINITION: When the OnStar® Call Center button is pressed, no connection is made to the OnStar® Call Center.
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	IMPORTANT: It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and global positioning system (GPS) data can be received from satellites. Press the OnStar® Call Center button. Wait for the system to either connect or end the call. Is a connection made with the OnStar® Call Center?	-	Go to Diagnostic Aids	Go to Step 3
3	Other than the normal progression tones of the system and the prompt Unable to Contact OnStar®, were any other tones or cellular messages heard?	-	Go to Step 4	Go to Step 5
4	IMPORTANT: Placing an emergency call to the OnStar® Call Center should only be made if the diagnosis of the system leads to this step. Immediately after an OnStar® advisor picks up the call, they should be told that this call is for diagnostic purposes only and there is no emergency. Record all messages heard from the OnStar® Call Center button press. Press the OnStar® emergency button. Does the emergency keypress call make a connection to the OnStar® Call Center within 10 minutes?	-	Have all messages heard during the course of the tests available, use the scan tool to access the STID, ESN and Transceiver I.D. and contact the General Motors Technical Assistance Center	Go to Step 5
5	Inspect the cellular antenna for exterior damage. Is the antenna assembly damaged?	-	Go to Step 9	Go to Step 6
6	IMPORTANT: Vehicle may be equipped with sectioned coax. Test each section and replace only the faulty section, not the entire length or coax. Disconnect the cellular antenna coax from the vehicle communication interface module (VCIM). Disconnect the cellular antenna coax from the cellular antenna. Measure the resistance from the center conductor of the coax to the metal outer shield. Does the meter read out of limits?	-	Go to Step 7	Go to Step 8
7	Measure the resistance of the cellular antenna coax center conductor from end to end. Does the resistance measure greater than the specified value?	1 Ω	Go to Step 8	Use the scan tool to access the STID, ESN and Transceiver I.D. and contact the General Motors Technical Assistance Center
8	Replace the cellular antenna coax. Did you complete the replacement?	-	Go to Step 10	-
9	Replace the cellular antenna assembly. Refer to Antenna Replacement - Cellular Communications/Digital Radio . Did you complete the replacement?	-	Go to Step 10	-
10	Operate the system in order to verify the repair. Did you correct the condition?	-	System OK	Go to Step 2