Buick Regal: DTC B0071

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 B0071 03

Passenger Seat Belt Tension Sensor Circuit Voltage Below Threshold

DTC B0071 04

Passenger Seat Belt Tension Sensor Circuit Open

DTC B0071 07

Passenger Seat Belt Tension Sensor Circuit Voltage Above Threshold

DTC B0071 08

Passenger Seat Belt Tension Sensor Circuit Voltage Performance - Signal Invalid

Diagnostic Fault Information

Circuit/System Description

The seat belt tension sensor is a 2-wire sensor mounted on the passenger seat belt retractor and provides an input to the passenger presence module. When an infant car seat is properly restrained on the front passenger seat, the seat belt is tightly secured through the car seat. The seat belt pulls on the tension sensor and changes the voltage signal to the passenger presence module. The passenger presence module monitors the belt tension sensor signal circuit and if a fault is detected, DTC will be set. When the passenger presence module detects this DTC it will send out a serial data message and the inflatable restraint sensing and diagnostic module will notify the customer of the enable/disable status by illuminating the OFF indicator on the PASSENGER AIR BAG ON/OFF indicators. The inflatable restraint sensing and diagnostic module will then suppress the deployment of the passenger instrument panel air bag and illuminate the AIR BAG indicator.

Conditions for Running the DTC

Ignition voltage is between 9 - 16 volts.

Conditions for Setting the DTC

• The passenger presence module detects the voltage at the passenger seat belt tension sensor signal circuit is less than 0.5 V or greater than 4.5 V for 1 s.
• The passenger presence module detects the voltage at the passenger seat belt tension sensor voltage reference circuit is less than 4.5 V or greater than 9.1 V for 1 s.
• The passenger presence module detects the amperage at the passenger seat belt tension sensor low reference circuit is 25 mA or greater for 1 s.

Action Taken When the DTC Sets

• The passenger presence module will set a DTC, and then communicate with the inflatable restraint sensing and diagnostic module.
• The inflatable restraint sensing and diagnostic module will set DTC B0081
• The inflatable restraint sensing and diagnostic module disables the passenger instrument panel air bag.
• The passenger presence module will illuminate the passenger air bag status OFF indicator.
• The inflatable restraint sensing and diagnostic module requests the instrument panel to illuminate the AIR BAG indicator.

Conditions for Clearing the DTC

• The condition for setting the DTC no longer exists.
• A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Diagnostic Aids

Inspect the passenger seat belt tension sensor signal and low reference circuits carefully for cutting and/or chafing.

Reference Information

Schematic Reference

SIR Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Supplemental Inflatable Restraint System Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Refer to Control Module References for scan tool information.

Circuit/System Testing

NOTE: The seat belt buckle replacement with the seat belt tension sensor must be serviced as a complete unit.

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

• Passenger seat belt tension sensor
• Passenger presence module
• Passenger seat belt tension sensor wiring harness connector
• Passenger presence module wiring harness connector

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B61P Seat Belt Tension Sensor - Passenger. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

• If greater than 10 Ω

1. Ignition OFF, disconnect the harness connector at the K85 Passenger Presence Module. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit and ground.
   • If less than 10 Ω, replace the K85 Passenger Presence Module.
   • If greater than 10 Ω, repair the open/high resistance.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for less than 6 V between the signal circuit terminal 1 and ground.

• If 6 V or greater

1. Ignition OFF, disconnect the harness connector at the K85 Passenger Presence 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.
   • If less than 1 V, replace the K85 Passenger Presence Module.

• Go to next step: If less than 6 V

5. Ignition OFF.

6. Test for greater than 5K Ω between the signal circuit terminal 1 and ground. It may take up to 2 minutes for all vehicle systems to power down.

• If less than 5K Ω

1. Disconnect the harness connector at the K85 Passenger Presence Module.
2. Test for Infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K85 Passenger Presence Module.

• Go to next step: If greater than 5K Ω

7. Disconnect the harness connector at the K85 Passenger Presence Module.

8. Test for less than 2 Ω between the B61P Seat Belt Tension Sensor - Passenger signal circuit terminal 1 and the K85 Passenger Presence Module signal circuit terminal 6.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

9. If all circuits test normal, replace the B61P Seat Belt Tension Sensor - Passenger.

10. Ignition ON, clear DTCs. Operate the vehicle within the Conditions for Running the DTC.

11. Verify DTC B0071 does not set.

• If DTC B0071 is set

Replace the K85 Passenger Presence Module.

• Go to next step: If DTC B0071 is not set

12. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Front Seat Belt Buckle Replacement for B61P Seat Belt Tension Sensor - Passenger
• Control Module References for passenger presence module replacement, programming, and setup

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