For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: OnStar Schematics Connector End View Reference: Entertainment/Communication Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Important: Contact the OnStar® Call Center first before pressing the emergency button in order to notify them of the test.

1. Turn ON the ignition, with the engine OFF.
2. Press each OnStar® button one at a time.

Are all buttons inoperative?

--

Go to Step 4

Go to Step 3

3 | Are any buttons intermittent or inoperative? | -- | Go to Step 7 | Go to Testing for Intermittent Conditions and Poor Connections
4 |

1. Turn OFF the ignition.
2. Disconnect the rearview mirror.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the keypad supply voltage circuit to a good ground.

Does the voltage measure greater than the specified value?

9 V

Go to Step 6

Go to Step 5

5 | Test the keypad supply voltage circuit for an open or short. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8
6 | Test the keypad signal circuit for an open or short . Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9
7 | Inspect for poor connections at the harness connector of the rearview mirror. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9
8 | Inspect for poor connections at the harness connector of the vehicle communication interface module (VCIM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10
9 | Replace the rearview mirror. Refer to Inside Rearview Mirror Replacement . Did you complete the replacement? | -- | Go to Step 11 | --
10 | Replace the VCIM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | --
11 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2