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.

### Circuit/System Description

The inflatable restraint sensing and diagnostic module (SDM) sends the status of the driver seat belt switch to the instrument panel cluster (IPC) via a GMLAN serial data message. If the seat belt is unfastened, the SDM will send a message to the IPC to illuminate the fasten safety belt indicator for 72 seconds or until the seat belt is fastened.

### Reference Information

#### Schematic Reference

• | Seat Belt Schematics

• | SIR Schematics

#### Connector End View Reference

Seat Belt Connector End Views

#### Description and Operation

Seat Belt System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Ignition ON, perform the IPC Display Test using the scan tool and verify the driver seat belt indicator is illuminated.

⇒ | If the indicator does not illuminate, replace the IPC.

### Circuit/System Testing

Important: When removing connectors inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector.

• | The BCM

• | The left seat belt switch

• | The SDM

• | The left seat belt switch harness connector

• | The SDM wiring harness connector

1. Ignition OFF, disconnect the harness connector at the left seat belt switch.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal A and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the SDM.

3. Ignition ON, verify the scan tool driver seat belt switch parameter is Unbuckled.

⇒ | If not the specified value, test the signal circuit terminal for a short to ground. If the circuit tests normal replace the SDM.

4. Install a 3-amp fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool driver seat belt switch parameter is Buckled.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the SDM.

5. If all circuits test normal, replace the left seat belt switch.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the left seat belt switch.
2. Test for infinite resistance between the signal circuit terminal B and the low reference terminal A.

⇒ | If not the specified value, replace the left seat belt switch.

3. With the seat belt buckled, test for less than 2 ohms of resistance between the signal circuit terminal B and the low reference terminal A.

⇒ | If greater than the specified range, replace the left seat belt switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Seat Belt Buckle Replacement

• | Control Module References for SDM and IPC replacement, setup, and programming