For 1990-2009 cars

#### Test Description

This procedure is for diagnosing conditions that will prevent OnStar® from powering up or the OnStar® button assembly telltale lamp from coming on. The following numbers refer to the steps in the table.

1. Determine if the OnStar® LED is inoperative.

2. Determine if the VIU has the necessary power circuit feeds.

3. Determine if the vehicle interface unit (VIU) has the necessary ground circuits.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the OnStar® Diagnostic System Check? | -- | Go to Step 2 | Go to OnStar System Check
2 |

1. Turn ON the ignition, with the engine OFF.
2. Activate the OnStar® call button.

Does "connecting to OnStar®" play throughout the audio system?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3 |

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

• | Measure the voltage from the ignition positive voltage circuit of the VIU to a good ground.

• | 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

4 | Repair the VIU feed circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | --
5 | Test the ground circuits of the VIU for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the problem? | -- | Go to Step 8 | Go to Step 6
6 | Inspect for poor connections at the harness connector of the VIU. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7
7 | Replace the VIU. Refer to OnStar Vehicle Interface Unit Replacement . Did you complete the replacement? | -- | Go to Step 8 | --
8 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2