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: 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
DTC B0072 05: Left Front Seat Belt Sensor Circuit Short to Battery or Open
DTC B0072 06: Left Front Seat Belt Sensor Circuit Short to Ground or Open
DTC B0072 08: Left Front Seat Belt Sensor Circuit Signal Invalid
DTC B0072 0B: Left Front Seat Belt Sensor Circuit Current Above Threshold
DTC B0072 0C: Left Front Seat Belt Sensor Circuit Current Below Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Left Front Seat Belt Sensor Signal | B0072 02, B0072 06, B0072 0B, 1 | B0072 04, B0072 05, B0072 06, B0072 0C, 2 | B0072 04, B0072 05, B0072 06, 2 | B0072 01, B0072 05, 2 | B0072 08
Left Front Seat Belt Sensor Low Reference | -- | B0072 04, B0072 05, B0072 06, B0072 0C, 2 | B0072 04, B0072 05, B0072 06, 2 | 2 | B0072 08
Right Front Seat Belt Sensor Signal | B0073 02, B0073 06, B0073 0B, 1 | B0073 04, B0073 05, B0073 06, B0073 0C, 2 | B0073 04, B0073 05, B0073 06, 2 | B0073 01, B0073 05, 2 | B0073 08
Right Front Seat Belt Sensor Low Reference | -- | B0073 04, B0073 05, B0073 06, B0073 0C, 2 | B0073 04, B0073 05, B0073 06, 2 | 2 | B0073 08
Left Rear Seat Belt Sensor Signal | B0075 02, B0075 06, B0075 0B | B0075 04, B0075 05, B0075 06, B0075 0C | B0075 04, B0075 05, B0075 06 | B0075 01, B0075 05 | B0075 08
Left Rear Seat Belt Sensor Low Reference | -- | B0075 04, B0075 05, B0075 06, B0075 0C | B0075 04, B0075 05, B0075 06 | -- | B0075 08
Right Rear Seat Belt Sensor Signal | B0076 02, B0076 06, B0076 0B | B0076 04, B0076 05, B0076 06, B0076 0C | B0076 04, B0076 05, B0076 06 | B0076 01, B0076 05 | B0076 08
Right Rear Seat Belt Sensor Low Reference | -- | B0076 04, B0076 05, B0076 06, B0076 0C | B0076 04, B0076 05, B0076 06 | -- | B0076 08
Center Rear Seat Belt Sensor Signal | B0077 02, B0077 06, B0077 0B | B0077 04, B0077 05, B0077 06, B0077 0C | B0077 04, B0077 05, B0077 06 | B0077 01, B0077 05 | B0077 08
Center Rear Seat Belt Sensor Low Reference | -- | B0077 04, B0077 05, B0077 06, B0077 0C | B0077 04, B0077 05, B0077 06 | -- | B0077 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 V.

### 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 04

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

#### B0072 05

The SDM detects the seat belt sensor circuit is shorted to battery or open for 2 seconds.

#### B0072 06

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

#### B0072 08

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

#### B0072 0B

The SDM detects the seat belt sensor signal circuit current is above threshold for 2 seconds.

#### B0072 0C

The SDM detects the seat belt sensor signal circuit current is below threshold for 2 seconds.

### Action Taken When the DTC Sets

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

• | The SDM will store the DTC.

### Conditions for Clearing the DTC

• | The condition for setting the DTC no longer exists.

• | A history DTC will clear once 100 fault-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

Ignition ON, observe the scan tool Driver Seat Belt Status parameter while buckling and unbuckling the seat belt. The reading should be Unbuckled 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

Note : 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 B88D driver seat belt switch.
2. Test for less than 1 Ω between low reference circuit terminal 2 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 K36 SDM.

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

⇒ | If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K36 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 Driver Seat Belt Status parameter is Unbuckled.

⇒ | 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 K36 SDM.

5. If the circuits test normal, replace the B88D driver seat belt switch.

### 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 ECM replacement, setup, and programming