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 Voltage
DTC B0072 02: Driver Seat Belt Sensor Circuit Short to Ground
DTC B0072 05: Driver Seat Belt Sensor Circuit Short to Battery or Open
DTC B0072 08: Driver Seat Belt Sensor Circuit Signal Invalid

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Seat Belt Sensor Driver Low Reference | -- | B0072 05, 2 | B0072 05, 2 | 2 | B0072 08
Seat Belt Sensor Driver Signal | B0072 02, 1 | -- | B0072 05, 2 | B0072 01, 2 | B0072 08
1. Indicator will remain ON with seat belt buckled 2. Indicator will illuminate only for the bulb test

### 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

The SDM detects the seat belt sensor circuit is shorted to voltage for 2 seconds.

#### B0072 02

The SDM detects the seat belt sensor circuit is shorted to ground for 2 seconds.

#### B0072 05

The SDM detects the seat belt sensor circuit is open for 2 seconds.

#### B0072 08

The SDM detects the seat belt sensor signal circuit is invalid for 2 seconds.

### Action Taken When the DTC Sets

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

• | The SDM will store the DTC.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present.

• | A history DTC will clear after 250 fault-free ignition cycles.

### Reference Information

#### Schematic Reference

SIR Schematics

#### Connector End View Reference

Component Connector End Views

#### 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 Verification

Ignition ON, observe the scan tool Driver Seat Belt Switch parameter while buckling and unbuckling the seat belt. The reading should be Not Buckled when the seat belt is unbuckled and the seat belt switch is closed. The reading should be Buckled when the seat belt is buckled and the seat belt switch is open.

### Circuit/System Testing

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

• | Seat belt sensor.

• | SDM.

• | Seat belt sensor wiring harness connector.

• | SDM wiring harness connector.

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

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

3. Ignition ON, verify the scan tool Driver Seat Belt switch parameter is Buckled.

⇒ | If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the SDM.

4. Connect a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Driver Seat Belt Switch parameter is Not Buckled.

⇒ | If not the specified value, test the signal circuit for short to voltage or an open/high resistance. If the circuit tests normal, replace the SDM.

5. If the circuits test normal, replace the seat belt buckle switch.

### Repair Instructions

perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Seat Belt Buckle Pretensioner Replacement.

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