For 1990-2009 cars

### 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.

### DTC Descriptor

DTC B2500 : Inflatable Restraint System Indicator Circuit

### Circuit/System Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

Upon passing these tests, ignition and deployment loop voltages are measured to ensure that they are within their normal voltage ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deployment loops.

If the warning lamp operates properly ON and OFF, the SDM measures the voltage continuously from the warning lamp terminal.

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

The warning lamp does not blink properly ON and OFF.

### Action Taken When the DTC Sets

The SDM commands the air bag indicator ON.

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

### 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

Note: 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. Disconnect the instrument cluster connector.
2. Ignition ON, check for 9-16V at terminal A35 of the cluster wiring connector.

⇒ | If voltage is not as specified, test circuit for an open, high resistance or short to ground.

3. Inspect the connection between terminal A35 and A27 of the cluster.

⇒ | If connection is not OK, replace the instrument cluster.

4. Ignition OFF, disconnect the connector of the sensing and diagnostic module (SDM).
5. Check for 0 ohms between terminal A27 of cluster connector and terminal 27 of the SDM connector.

⇒ | If resistance is not as specified, test circuit for an open or high resistance.

6. Check for infinite ohms between terminal 27 of the SDM connector and ground, battery positive.

⇒ | If resistance is not as specified, test circuit for a short to ground or short to voltage.

⇒ | If resistance is as specified, replace the SDM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for SDM replacement, setup, and programming