For 1990-2009 cars

The following diagnostic procedure must be used when all circuitry outside the sensing and diagnostic module (SDM) has been found to operate properly, as indicated by following the appropriate DTC table. The procedure verifies the need for SDM replacement.

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Circuit/System Description

When the SDM recognizes ignition voltage greater than 9 volts at the SDM, the air bag indicator flashes 6 times to verify operation. At this time the SDM performs turn-on tests followed by resistance measurement tests and continuous monitoring tests.

When malfunction is detected, the SDM sets a current DTC and illuminates the air bag indicator.

When the malfunction is no longer detected and/or the ignition switch is cycled, the SDM will clear current DTCs and move them to a history file, except for the DTCs B1620, B1650, B1651, B1652, B1657. These DTCs will not be cleared by a scan tool because these codes require replacement of the SDM. The SDM must be replaced only after the malfunction that set the DTC has been repaired.

### 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

### 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.

• | The I/P module

• | The SDM module

• | The I/P wiring harness connector

• | The SDM wiring harness connector

1. Turn the ignition to LOCK and remove the key.
2. Connect all supplemental inflatable restraint (SIR) components and ensure that all the components are properly mounted.
3. Ensure that the ignition switch has been OFF for at least 30 seconds.
4. Ignition ON, observe the air bag indicator flashes 6 times.

⇒ | If air bag indicator does not flash 6 times, and same DTC is set again, replace the SDM.

⇒ | If air bag indicator does not flash 6 times, and different DTC is set then previous, refer to Diagnostic System Check - Vehicle.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for SDM replacement, setup, and programming