DEFINITION: This procedure is for diagnosing conditions that will prevent OnStar® from powering up or the OnStar® Button Assembly Telltale Lamp from coming on.

Did you perform the OnStar® Diagnostic System Check?

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Go to Step 2

Go to OnStar System Check

Refer to OnStar Operation operation.

Does the OnStar® system operate correctly?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

1. Turn ON the ignition, with the engine OFF.
2. Using a DMM;

2.1.	Measure the voltage from the Ignition Positive Voltage circuit of the VIU to a good ground.

2.2.	Measure the voltage from the Positive Battery Voltage circuit of the VIU to a good ground.

Does the voltage measure near the specified Value?

12V

Go to Step 5

Go to Step 4

Repair the affected VIU feed circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 7

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5

Test the Ground circuits of the VIU for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the problem?

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Go to Step 7

Go to Step 6

Replace the Vehicle Interface Unit (VIU). Refer to Vehicle Interface Unit and Vehicle Communication Unit Modules Replacement .

Did you complete the replacement?

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Go to Step 7

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2