Buick Regal: Symptoms - Seat Belts

NOTE: Review the seat belt system description and operation in order to familiarize yourself with the system and how it functions.

Visual/Physical Inspection

• Inspect for aftermarket devices which could affect the operation of the seat belt system. Refer to Checking Aftermarket Accessories.
• Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections.

Symptom List

Refer to the following symptom diagnostic procedure in order to diagnose the symptom:

• Seat Belt Indicator Malfunction - Driver
• Seat Belt Indicator Malfunction - Passenger

SEAT BELT INDICATOR MALFUNCTION - DRIVER

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

1. Seat Belt Indicator Always Illuminated
2. Seat Belt Indicator Inoperative

Circuit/System Description

The driver seat belt 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. The SDM sends the status of the driver seat belt via serial data to the instrument cluster. After receiving the message, the instrument cluster controls the illumination of the driver seat belt indicator.

Reference Information

Schematic Reference

• Seat Belt Wiring Schematics
• SIR Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

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

Control Module References for scan tool information

Circuit/System Verification

1. Command the instrument cluster all indicators ON and OFF with a scan tool. The driver seat belt indicator should turn ON and OFF as commanded.

• If the driver seat belt indicator does not turn ON and OFF as commanded

Replace the P16 instrument cluster.

• Go to next step: If the driver seat belt indicator does turn ON and OFF as commanded

2. Monitor the scan tool Driver Seat Belt Switch parameter while buckling and unbuckling the seat belt. The parameter should display Buckled and Unbuckled when changing seat belt states.

• If the scan tool Driver Seat Belt Switch parameter does not display Buckled and Unbuckled when changing seat belt states

Refer to Circuit/System Testing.

• Go to next step: If the scan tool Driver Seat Belt Switch parameter does display Buckled and Unbuckled when changing seat belt states

3. All OK.

Circuit/System Testing

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

• B88 Seat belt switch
• Seat belt switch harness connector
• K36 SDM
• SDM wiring harness connector

1. Ignition OFF.

2. Disconnect the harness connector at the B88 seat belt switch.

3. Test for less than 10 Ω between the low reference circuit terminal 1 and ground.

• If 10 Ω or greater

1. Disconnect the harness connector at the K36 SDM.
2. Test for less than 2 Ω in each control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K36 SDM.

• Go to next step: If less than 10 Ω

4. Ignition ON.

5. Verify the scan tool Driver Seat Belt Status parameter displays Buckled.

• If the scan tool Driver Seat Belt Status parameter does not display Buckled

1. Disconnect the harness connector at the K36 SDM.
2. Test for infinite resistance between the seat belt switch signal circuit terminal 2 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If less than 2 Ω, replace the K36 SDM.

• Go to next step: If the scan tool Driver Seat Belt Status parameter does display Buckled

6. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1.

7. Verify the scan tool Driver Seat Belt Status parameter displays Unbuckled.

• If the scan tool Driver Seat Belt Status parameter does not display Unbuckled

1. Disconnect the harness connector at the K36 SDM.
2. Ignition ON.
3. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
4. Test for less than 2 Ω in each circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K36 SDM.

• Go to next step: If the scan tool Driver Seat Belt Status parameter does display Unbuckled

8. Replace the B88 seat belt switch.

Component Testing

1. Ignition OFF.

2. Disconnect the harness connector at the B88 seat belt switch.

3. B88 seat belt switch in the open position.

4. Test for infinite resistance between the signal circuit terminal 2 and the low reference terminal 1 at the B88 seat belt switch.

• If there is not infinite resistance

Replace the B88 seat belt switch.

• Go to next step: If there is infinite resistance

5. B88 seat belt switch in the closed position.

6. Test for less than 1 Ω between the signal circuit terminal 2 and the low reference terminal 1 at the B88 seat belt switch.

• If 1 Ω or greater

Replace the B88 seat belt switch.

• Go to next step: If less than 1 Ω

7. All OK.

Repair Instructions

• Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• Front Seat Belt Buckle Replacement
• Control Module References for SDM and instrument cluster replacement, programming and setup

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