For 1990-2009 cars

### 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

### Circuit/System Description

The inflatable restraint seat belt switch is within the seat belt retractor 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

#### Electrical Information Reference

• | Circuit Testing

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Connector Repairs

### Circuit/System Testing

Important: The seat belt switch is not serviced separately. The seat belt retractor with the seat belt 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 switch wiring harness connector

• | Seat belt switch

• | SDM wiring harness connector

1. Ignition OFF, disconnect the seat belt switch connector.
2. Test for less than 1 ohm between low reference terminal A and ground.

⇒ | If greater than specified, test the low reference circuit for open/high resistance. If the circuit tests normal, replace the SDM.

3. Ignition ON. Test for 1.0-1.6 volts between the signal circuit terminal B and ground.

⇒ | If less that the specified range, test the signal circuit for open/high resistance or a short to ground. If the circuit tests normal, replace the SDM.

⇒ | If greater that the specified range, test the signal circuit for a short to voltage.

4. If the circuits test normal, replace the seat belt retractor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Seat Belt Retractor Pretensioner Replacement - Front

• | SIR/SRS Wiring Repairs

• | Control Module References for SDM and PPS replacement, setup, and programming