Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Aids
2002 Chevrolet Avalanche 2500, RWDSECTION Diagnostic Aids
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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 customers 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 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
| Step | Action | Value | Yes | No |
|---|---|---|---|---|
| Schematic Reference: OnStar Schematics Connector End View Reference: Cellular 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 cellular Communication Diagnostic System Check? | - | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication |
| 2 |
IMPORTANT:
It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and GPS data can be received from satellites.
|
- | 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.
|
- | 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 and navigation antenna for exterior damage. Is the antenna assembly damaged? |
- | Go to Step 9 | Go to Step 6 |
| 6 |
|
- | 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 and navigation antenna assembly. Refer to Antenna Assembly Replacement - Cellular and Navigation . 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 |
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.