Buick Regal: DTC B0075-B0077

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

DTC Descriptors

DTC B0075

Left Rear Seat Belt Switch Circuit

DTC B0076

Right Rear Seat Belt Switch Circuit

DTC B0077

Center Rear Seat Belt Switch Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The inflatable restraint seat belt buckle switch is within the seat belt buckle and provides an input to the Inflatable Restraint Sensing and Diagnostic Module (SDM). The Inflatable Restraint Sensing and Diagnostic Module supplies a low reference circuit and a seat belt switch signal circuit to determine a buckled or unbuckled condition. The Inflatable Restraint Sensing and Diagnostic Module monitors the seat belt switch circuits and if a fault is detected a DTC will be set.

Conditions for Running the DTC

Ignition voltage is between 9 - 16 V.

Conditions for Setting the DTC

B0075 01, B0076 01, or B0077 01

The seat belt switch circuit is shorted to voltage.

B0075 02, B0076 02, or B0077 02

The seat belt switch circuit is shorted to ground.

B0075 04, B0076 04, or B0077 04

The seat belt switch circuit is open.

B0075 05, B0076 05, or B0077 05

The seat belt switch circuit is shorted to voltage or open.

B0075 06, B0076 06, or B0077 06

The seat belt switch circuit is shorted to ground or open.

B0075 08, B0076 08, or B0077 08

The seat belt switch signal is invalid.

B0075 0B, B0076 0B, or B0077 0B

The seat belt switch signal is above threshold.

B0075 0C, B0076 0C, or B0077 0C

The seat belt switch signal is below threshold.

Action Taken When the DTC Sets

The Inflatable Restraint Sensing and Diagnostic Module will store a DTC and illuminate the Air Bag indicator in the instrument cluster.

Conditions for Clearing the DTC

The condition for setting the DTC no longer exists.

Reference Information

Schematic Reference

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
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Connector Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Verify the appropriate scan tool Seat Belt Status parameter changes between Buckled and Unbuckled when the seat belt is buckled and unbuckled.

• If the parameter does not change

Refer to Circuit/System Testing.

• Go to next step: If the parameter changes

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.

• B88RR Seat Belt Switch-Right Rear
• B88A Seat Belt Switch-Rear Middle Left
• K36 Inflatable Restraint Sensing and Diagnostic Module

1. Ignition OFF, disconnect the harness connector at the appropriate B88 seat belt switch.

2. Test for less than 5 Ω between the low reference circuit terminal 2 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K36 Inflatable Restraint Sensing and Diagnostic Module.
2. Test for less than 2 Ω in the low reference 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 Inflatable Restraint Sensing and Diagnostic Module.

• Go to next step: If less than 5 Ω

3. Ignition ON.

4. Verify the appropriate scan tool Seat Belt Status parameter is Buckled.

• If not Buckled

1. Ignition OFF, disconnect the harness connector at the K36 Inflatable Restraint Sensing and Diagnostic Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K36 Inflatable Restraint Sensing and Diagnostic Module.

• Go to next step: If Buckled

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

6. Verify the appropriate scan tool Seat Belt Status parameter is Unbuckled.

• If not Unbuckled

1. Ignition OFF, disconnect the harness connector at the K36 inflatable restraint sensing and diagnostic module, ignition ON.
2. 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.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal 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 inflatable restraint sensing and diagnostic module.

• Go to next step: If Unbuckled

7. Test or replace the B88 Seat Belt Switch.

Component Testing

1. Ignition OFF, disconnect the harness connector at the B88 Seat Belt Switch.

2. Test for infinite resistance between the signal terminal 1 and the low reference terminal 2.

• If less than infinite resistance

Replace the B88 Seat Belt Switch.

• Go to next step: If infinite resistance

3. Insert the seat belt into the buckle.

4. Test for less than 5 Ω between the signal terminal 1 and the low reference terminal 2.

• If 5 Ω or greater

Replace the B88 Seat Belt Switch.

• Go to next step: If less than 5 Ω

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Front Seat Belt Buckle Replacement
• Rear Seat Belt Buckle Replacement
• SIR/SRS Wiring Repairs
• Control Module References for inflatable restraint sensing and diagnostic module replacement, setup, and programming

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