Diagnostic Instructions

DTC Descriptors

DTC B0072 01: Left Front Seat Belt Sensor Circuit Short to Battery

DTC B0072 02: Left Front Seat Belt Sensor Circuit Short to Ground

DTC B0072 04: Left Front Seat Belt Sensor Circuit Open Circuit

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

DTC B0072 08: Left Front Seat Belt Sensor Circuit Signal Invalid

DTC B0073 01: Right Front Seat Belt Sensor Circuit Short to Battery

DTC B0073 02: Right Front Seat Belt Sensor Circuit Short to Ground

DTC B0073 04: Right Front Seat Belt Sensor Circuit Open Circuit

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

DTC B0073 08: Right Front Seat Belt Sensor Circuit Signal Invalid

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Driver Seat Belt Switch Signal	B0072 02	B0072 04	B0072 01	B0072 08
Passenger Seat Belt Switch Signal	B0073 02	B0073 04	B0073 01	B0073 08
Low Reference	--	B0072 04, B0073 04	--	--

Circuit/System Description

The seat belt buckle switch is located within the seat belt buckle assembly 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.

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 is shorted to voltage for 500 milliseconds.

B0072 02, B0073 02

The SDM detects the seat switch signal 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 is 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 commands the AIR BAG indicator ON.

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Seat Belt Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the appropriate scan tool Seat Belt Switch parameter while buckling and unbuckling the seat belt. The parameter should change between Buckled and Unbuckled.

Circuit/System Testing

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

•	The SDM wiring harness connector

•	The seat belt buckle

•	The seat belt buckle wiring harness connector

1. Ignition OFF, disconnect the harness connector of the seat belt switch.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal A 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 appropriate scan tool Seat Belt Switch parameter is Unbuckled.

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

4. Install a 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the appropriate scan tool Seat Belt Switch parameter is Buckled.

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

5. If all circuits test normal, test or replace the seat belt buckle assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.