For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Keypad Supply Voltage | B2476 00 | B2476 00 | B2476 00 | --
Keypad Green LED Signal | 1 | 1 | 2 | --
Keypad Red LED Signal | 1 | 1 | 2 | --
Keypad Signal | 3 | 3 | -- | --
Inside Rearview Mirror Ground | -- | 1 | -- | --
1. OnStar® LED Inoperative 2. LED Illuminated At All Times 3. OnStar® Buttons Inoperative

### Circuit Description

The OnStar® status LEDs are located with the OnStar buttons.. The green LED is illuminated when the system is ON and operating normally. When the green LED is green and flashing, it is an indication that a call is in progress. When the red LED is illuminated, a system malfunction is present. In the event there is a system malfunction and the OnStar® system is still able to make a call, the LED will flash red during the call. The OnStar® LEDs are controlled by the communication interface module (CIM) via the keypad green LED signal circuit and the keypad red LED signal circuit.

### Reference Information

#### Schematic Reference

OnStar Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

OnStar Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, command the Green LED ON and OFF with a scan tool while observing the green LED on the inside rearview mirror. The green LED should turn ON and OFF when commanded.
2. Command the red LED ON and OFF with a scan tool while observing the red LED on the inside rearview mirror. The red LED should turn ON and OFF when commanded.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Doors closed, courtesy lamps OFF, test for less than 5 ohms between the ground circuit terminal 8 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, command the green LED OFF with a scan tool. Test for less than 1 volt between the control circuit terminal 14 and ground.

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the CIM.

4. Command the green LED ON with a scan tool. Test for greater than 9 volts between the control circuit terminal 14 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CIM.

5. Command the red LED OFF with a scan tool. Test for less than 1 volt between the control circuit terminal 15 and ground.

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the CIM.

6. Command the red LED ON with a scan tool. Test for greater than 9 volts between the control circuit terminal 15 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CIM.

7. If all circuits test normal, replace the inside rearview mirror.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inside Rearview Mirror Replacement

• | Control Module References for CIM replacement, setup, and programming