For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: OnStar Schematics Connector End View Reference: Cellular Communication Connector End Views
1 | Did you perform the Cellular Communication Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication
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 in Wiring Systems
4 |

1. Turn OFF the ignition.
2. Disconnect the rear view 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Stationary Windows. Did you complete the replacement? | -- | Go to Step 11 | --
10 | Important: Perform the OnStar® setup procedure. Replace the VCIM. Refer to Communication Interface Module Replacement . 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