GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Impala 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 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 07: Passenger Seat Belt Tension Sensor Circuit Voltage Above Threshold

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Belt Tension Sensor Signal

B0071 03

B0071 03, 07

B0071 03, 07

B0071 07

Belt Tension Sensor Voltage Reference

B0071 03

B0071 03

B0071 03

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Belt Tension Sensor Low Reference

--

B0071 07

B0071 07

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Circuit/System Description

The inflatable restraint seat belt tension sensor is a 3-wire potentiometer mounted on the buckle side of the passenger seat belt and provides an input to the passenger presence system (PPS). 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 PPS module. The PPS monitors the belt tension sensor signal circuit and if a fault is detected, DTC will be set. When the PPS detects this DTC it will send out a serial data message and the SDM will notify the customer of the enable/disable status by illuminating the OFF indicator on the PASSENGER AIR BAG ON/OFF indicators. The SDM will then suppress the deployment of the instrument panel (I/P) module and illuminate the AIR BAG indicator.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC
    • The PPS detects the voltage at the belt tension sensor signal circuit is less than 0.5 volt or greater than 4.5 volts for 1 second.
    • The PPS detects the voltage at the belt tension sensor voltage reference circuit is less than 4.5 volts or greater than 9.1 volts for 1 second.
    • The PPS detects the amperage at the belt tension sensor low reference circuit is 25 mA or greater for 1 second.

Action Taken When the DTC Sets
    • The PPS will set a DTC, and then communicate with the SDM.
    • The SDM will request the instrument panel cluster (IPC) to illuminate the PASSENGER AIRBAG OFF indicator.
    • The SDM requests the IPC to illuminate the AIR BAG indicator.
    • The SDM will set DTC B0081 0F in addition to the PPS DTC.

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, voltage reference, and low reference circuits carefully for cutting and/or chafing.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR 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 Testing

Important: The seat belt tension sensor is not serviced separately. The seat belt buckle replacement with the seat belt tension sensor must be serviced as a complete unit.

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

   • Seat belt tension sensor
   • PPS module
   • Seat belt tension sensor wiring harness connector
   • PPS module wiring harness connector

  1. Ignition OFF, disconnect the harness connector at the seat belt tension sensor and inspect the component and harness sides for damage or corrosion.
    2. ⇒If damage or corrosion is found, repair or replace as necessary.
  2. Ignition ON, test for 4.5-5.5 volts between the voltage reference circuit terminal A and ground.
    3. ⇒If less that the specified range, test the voltage reference circuit for open/high resistance or a short to ground. If the circuit tests normal, replace the PPS.
    ⇒If greater that the specified range, test the voltage reference circuit for a short to voltage. If the circuit tests normal, replace the PPS.

    Important: The AIR BAG Fuse that supplies B+ voltage must be removed to ensure the PPS module is inactive. An active PPS module may cause inaccurate resistance readings.

  3. Ignition OFF, remove the AIRBAG Fuse. Test for less than 2.0 ohms between low reference terminal B and ground.
    4. ⇒If greater than the specified range, test the low reference circuit for open/high resistance. If the circuit tests normal, replace the PPS.
  4. Ignition OFF, disconnect the harness connector at the PPS module.
  5. Test for infinite resistance between the signal circuit terminal C and ground.
    6. ⇒If less than the specified value, test the signal circuit for a short to ground.
  6. Ignition ON, test for less than 1 volt between the signal circuit terminal C and ground.
    7. ⇒If greater than the specified range, test the signal circuit for a short to voltage.
  7. Test for less than 1 ohm in the signal circuit between PPS module terminal 4 and belt tension sensor terminal C.
    8. ⇒If greater than the specified range, test the signal circuit for open/high resistance. If the circuit tests normal, replace the PPS.
  8. If all circuits test normal, replace the passenger seat belt buckle which includes the seat belt tension sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Seat Belt Buckle Replacement
    •  SIR/SRS Wiring Repairs
    •  Control Module References for PPS replacement, setup, and programming