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 passenger seat belt switch to the body control module (BCM) via the GMLAN serial data communication line. The BCM controls power to the passenger seat belt indicator to turn the indicator on/off. The SDM will only send a command to the BCM to turn the indicator on when the seat belt is unbuckled and the SDM senses an occupant in the passenger seat.

### 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

1. Ignition ON, command the Passenger Seat Belt Reminder LED ON and OFF with a scan tool. The passenger seat belt indicator should turn ON and OFF as commanded.

⇒ | If the indicator does not turn ON and OFF with each command, refer to Passenger Seat Belt Indicator Malfunction.

2. While sitting in the passenger seat, fasten the passenger seat belt. The passenger seat belt indicator should turn off.

⇒ | If the indicator remains illuminated, refer to Seat Belt Switch Malfunction.

### 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 right seat belt switch

• | The SDM

• | The right seat belt switch harness connector

• | The SDM wiring harness connector

#### Passenger Seat Belt Indicator Malfunction.

1. Ignition OFF, disconnect the harness connector at the Inflatable Restraint PASSENGER AIRBAG ON/OFF Indicator.
2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 4 and ground.

⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Connect a test lamp between the ignition circuit terminal 4 and the control circuit terminal 5.
4. Command the Passenger Seat Belt Reminder LED ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the Inflatable Restraint PASSENGER AIRBAG ON/OFF Indicator.

#### Seat Belt Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the right seat belt switch.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal C 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 and sitting in the passenger seat, verify the scan tool passenger seatbelt indicator commanded parameter reads ON.

⇒ | 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 A and the low reference circuit terminal C. While sitting in the passenger seat, verify the scan tool passenger seatbelt indicator commanded parameter reads OFF.

⇒ | 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 right seat belt switch.

### Component Testing

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

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

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

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Seat Belt Buckle Replacement

• | Inflatable Restraint Instrument Panel Module Indicator Replacement

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