For 1990-2009 cars
Cellular Communication Component Views
Onstar Schematics

### Circuit Description

The OnStar® button assembly consists of three buttons: Call/Answer, OnStar® Call Center and OnStar® Emergency. Ten volts is supplied to the button assembly on the keypad supply voltage circuit. Each of the buttons, when pressed, completes the circuit across a resister allowing a specific voltage to be returned to the vehicle communication interface module (VCIM) on the keypad signal circuit. Depending upon the voltage range returned, the vehicle communication interface module (VCIM) is able to identify which button has been pressed.

### Conditions for Running the DTC

• | The ignition must be in the RUN or ACC position.

• | The system voltage is at least 9.5 volts and no more than 15.5 volts.

• | All the above conditions are present for greater than 300 ms.

### Conditions for Setting the DTC

• | The VCIM powers the button assembly through the Keypad Supply Voltage circuit, turns the power OFF, then waits for 10 ms and sees a voltage value greater than 5 volts on this circuit.

• | The above conditions are present for greater than 300 ms.

### Action Taken When the DTC Sets

• | The VCIM will ignore all inputs from the OnStar® button assembly.

• | No calls can be placed.

• | The OnStar® status LED turns RED.

### Conditions for Clearing the DTC

• | The VCIM powers the button assembly through the Keypad Supply Voltage circuit, turns the power OFF, then waits for 10 ms and sees a voltage value less than 5 volts on this circuit.

• | A history DTC clears after 50 malfunction free ignition cycles.

• | The VCIM receives the clear DTC command from the scan tool.

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step checks that the VCIM is sending out the proper supply voltage.

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 Communications Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication
2 |

1. Turn OFF the ignition.
2. Disconnect the rearview mirror assembly connector.
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 4

Go to Step 3

3 | Test the keypad supply voltage circuit for an open or short to ground. 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
4 | Test the keypad supply voltage circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 5
5 | Test the keypad ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 6
6 | Test the keypad signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7
7 | Inspect for poor connections at the harness connector of the rear view 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 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK