For 1990-2009 cars

### Circuit 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.

### DTC Descriptor

This diagnostic procedure supports the following DTCs:

DTC 031 SDM Not Reusable

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

The SDM does not implement diagnostic operation. The wiring harness of the SDM should be inspected before replacing the SDM.

### 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.

Step | Action | Yes | No
--- | --- | --- | ---
Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section. Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section. Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views
1 | Did you perform a Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Disconnect the negative battery cable.
2. Wait 1 minute for the sensing and diagnostic module (SDM) capacitor to discharge.
3. Visually inspect the SIR wiring harness.

Is there any visible damage to the SIR harness?

Go to Step 4

Go to Step 3

3 | Replace the SDM. Did you complete the repair? | Go to Step 5 | --
4 | Replace the SIR wiring harness. Did you complete the repair? | Go to Step 5 | --
5 |

1. Reconnect all SIR components.
2. Verify that all components, connectors and connector position assurances (CPAs) are properly mounted.
3. Use the scan tool in order to clear the DTCs.
4. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK