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 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 Right Signal | B0073 02, B0073 06 | B0073 04 | B0073 04 | B0073 01 | B0073 08
Seat Belt Switch Low Reference | -- | B0073 04 | B0073 04 | -- | B0073 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

#### B0073 01

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

#### B0073 02

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

#### B0073 04

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

#### B0073 06

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

#### B0073 08

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

### Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

### 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

• | SIR Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

SIR 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 Verification

1. Ignition ON, with a scan tool perform the instrument panel cluster (IPC) Display Test and verify the passenger seat belt indicator is illuminated for 5 seconds.

⇒ | If the indicator does not illuminate, replace the IPC.

2. Monitor the SDM Passenger Seat Belt Switch parameter while connecting and disconnecting the seat belt. The parameter should display Buckled and Unbuckled when changing seat belt states.

### Circuit/System Testing

Important:

• | Refer to SIR Service Precautions

• | 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:

- | The SDM

- | The seat belt buckle switch wiring harness connector

- | The seat belt buckle switch

- | The SDM wiring harness connector

1. Ignition OFF, disconnect the harness connector of the seat belt switch.
2. Test for less than 1.0 ohm between low reference terminal 2 and ground.

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

3. Ignition ON, with the passenger seat belt unbuckled, verify the scan tool Passenger Seat Belt Switch parameter is Unbuckled.

⇒ | If not the specified value, test the signal circuit terminal 1 for short to ground. If the circuit tests normal, replace the SDM.

4. Connect a 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool Passenger Seat Belt Switch parameter is 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.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the seat belt switch.
2. With the seat belt buckled, test for infinite resistance between the signal circuit terminal 1 and the low reference terminal 2.

⇒ | If not the specified range, replace the seat belt switch.

3. With the seat belt unbuckled, test for less than 2 ohms between the signal circuit terminal 1 and the low reference terminal 2.

⇒ | If greater than the specified range, replace the seat belt switch.

### 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 SDM replacement, setup, and programming