GM Service Manual Online
For 1990-2009 cars only

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 B0072 01: Driver Seat Belt Sensor Circuit Short to Battery

DTC B0072 02: Driver Seat Belt Sensor Circuit Short to Ground

DTC B0072 04: Driver Seat Belt Sensor Circuit Open Circuit

DTC B0072 06: Driver Seat Belt Sensor Circuit Short To Ground or Open Circuit

DTC B0072 08: Driver Seat Belt Sensor Circuit Signal Invalid

DTC B0073 01: Passenger Seat Belt Sensor Circuit Short to Battery

DTC B0073 02: Passenger Seat Belt Sensor Circuit Short to Ground

DTC B0073 04: Passenger Seat Belt Sensor Circuit Open Circuit

DTC B0073 06: Passenger Seat Belt Sensor Circuit Short To Ground or Open Circuit

DTC B0073 08: Passenger Seat Belt Sensor Circuit Signal Invalid

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

Seat Belt Switch Left Signal

B0072 02, 06

B0072 04

B0072 04

B0072 01

B0072 08

Seat Belt Switch Right Signal

B0073 02, 06

B0073 04

B0073 04

B0073 01

B0073 08

Seat Position Sensor Low Reference

--

B0072 04, B0073 04

B0072 04, B0073 04

--

B0072 08

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 SDM supplies a low reference circuit and a seat belt switch signal circuit to determine a buckled or unbuckled condition. The SDM 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 volts.

Conditions for Setting the DTC

B0072 01, B0073 01

The SDM detects the seat switch signal circuit or low reference circuit is shorted to voltage for 500 milliseconds.

B0072 02, B0073 02

The SDM detects the seat switch signal circuit or low reference circuit is shorted to ground for 500 milliseconds.

B0072 04, B0073 04

The SDM detects the seat switch signal circuit or low reference circuit is open for 500 milliseconds.

B0072 06, B0073 06

The SDM detects the seat switch signal circuit or low reference circuit is shorted to ground or an open for 500 milliseconds.

B0072 08, B0073 08

The SDM detects an invalid signal in the seat switch signal circuit.

Action Taken When the DTC Sets

    • The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator.
    • The SDM will store a 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.

Reference Information

Schematic Reference

Seat Belt Schematics

Connector End View Reference

Component Connector End Views

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 Testing

Important: The seat belt buckle switch is not serviced separately. The seat belt buckle with the seat belt buckle switch 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:

   • SDM module
   • Seat belt buckle switch wiring harness connector
   • Seat belt buckle switch
   • SDM wiring harness connector

  1. Ignition OFF, disconnect the harness connector at the seat belt switch.
  2. Test for less than 1.0 ohm between the low reference terminal A and ground.
  3. If greater than specified, test the low reference circuit for open/high resistance. If the circuit tests normal, replace the SDM.
  4. Ignition ON, test for 1.0-1.6 volts between the signal circuit terminal B and ground.
  5. If less that the specified range, test the signal circuit for a short to ground or for an open/high resistance. If the circuit tests normal, replace the SDM.
    If greater that the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the SDM.
  6. If all circuits test normal, replace the seat belt buckle.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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