The seat belt buckle switch is a 2-wire switch wired to the inflatable restraint sensing and diagnostic module (SDM) using a signal circuit and a low reference circuit. When the seat belt is unbuckled the switch is closed, and when the seat belt is buckled the switch is open. When the passenger presence system (PPS) indicates that the seat is occupied, the SDM sends the status of the passenger seat belt via serial data to the instrument panel cluster (IPC). After receiving the message, the IPC controls the illumination of the passenger seat belt indicator by grounding the indicator control circuit. If an occupant is seated in the front passenger seat and the seat belt is unfastened, the SDM will send a message to the IPC to illuminate the fasten seat belt indicator for approximately 72 seconds or until the seat belt is fastened.

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

Seat Belt System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information

1. With no weight in the passenger seat observe the passenger seat belt status indicator. Turn ON the ignition, the indicator should illuminate for 5 seconds.

⇒	If the indicator is always ON or always OFF, refer to Indicator Circuit Test.

2. Ignition ON, monitor the Passenger Seat Belt Switch parameter while connecting and disconnecting the seat belt. The parameter should display Buckled and Unbuckled when changing seat belt states.

⇒	If the parameter displays incorrectly, refer to Switch Circuit Test.

Indicator Circuit Test

1. Ignition OFF, disconnect the harness connector at the inflatable restraint passenger air bag 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. If the circuit tests normal and the ignition circuit fuse is open, test or replace the inflatable restraint passenger air bag ON/OFF indicator.

3. Connect a test lamp between the control circuit terminal 5 and the ignition circuit terminal 4.

Important: Allow 5 seconds after seat is occupied for test lamp to change states.

4. With the passenger seat occupied the test lamp should turn ON with the seat belt disconnected, and turn OFF with the seat belt connected.

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

⇒	If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the IPC.

5. If the circuits test normal, replace the inflatable restraint passenger air bag ON/OFF indicator.

Switch Circuit Test

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 seat belt switch

•	The seat belt switch harness connector

•

The SDM

•	The SDM harness connector

1. Ignition OFF, disconnect the harness connector at the seat belt switch.
2. Test the resistance between the low reference circuit terminal B X1 and signal circuit terminal A X1 of the switch (buckle side) while connecting and disconnecting the seat belt. The resistance should switch between infinity and less than 2 ohms.

⇒	If not as specified, replace the seat belt buckle.

3. Ignition ON, using a scan tool, verify the Passenger Seat Belt Switch parameter display is Buckled.

⇒	If the parameter is Unbuckled, test the seat belt switch signal circuit 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 X1 and the low reference circuit terminal B X1. Verify the scan tool Passenger Seat Belt Switch parameter display is Unbuckled.

⇒	If the parameter is Buckled, test the signal and the low reference circuits for open/high resistance. If the circuits test normal, replace the SDM.

1. Ignition OFF, disconnect the harness connector at the seat belt switch.
2. With the seat belt buckled, test for infinite resistance between the signal circuit terminal A X1 and the low reference terminal B X1.

⇒	If not the specified range, replace the seat belt switch.

3. With the seat belt unbuckled, test for less than 2 ohms between the signal circuit terminal A X1 and the low reference terminal B X1.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.