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.

### Circuit Description

When the ignition is turned ON, the instrument panel cluster (IPC) flashes the AIR BAG indicator seven times. The inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within the SIR system. If no SIR system malfunctions exists, the SDM will request the IPC to turn the AIR BAG indicator OFF after it has flashed 7 times. The AIR BAG indicator is controlled by the SDM via class 2 serial data.

### Diagnostic Aids

• | If ignition 1 voltage for the SDM is outside of the normal operating voltage range (9-16 volts), the AIR BAG indicator will come ON solid with no DTC set.

• | The loss of serial data communication between the SDM and the IPC will cause the AIR BAG indicator to come ON solid. Refer to DTC U1001-U1254 .

### Reference Information

#### Schematic Reference

SIR Schematics

#### Connector End View Reference

SIR Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

1. With the ignition ON, with a scan tool, request the ignition voltage parameter in the SIR data list. If the parameter does not read 9-16 volts, test the ignition 1 voltage for a short to voltage, open/high resistance or a short to ground.

⇒ | If a condition exists, make the appropriate repair.

2. With the ignition OFF, test the SDM ground circuit for an open or high resistance.

⇒ | If a condition exists, make the appropriate repair

3. Remove the inflatable restraint SDM connector. Inspect the SDM connector for damage or corrosion that may cause a malfunction.

⇒ | If damage or corrosion is found make the appropriate repair.

4. Replace the SDM.
5. If replacement of the SDM does not repair the vehicle, replace the IPC.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | SIR/SRS Wiring Repairs

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