For 1990-2009 cars

### Circuit Description

When the ignition is first turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM is hard-wired to the body control module (BCM) through the deployment commanded output (DCO) circuit. During CONTINUOUS MONITORING, the SDM sends fixed frequency pulses to the BCM. In the event of a collision involving inflator module or seat belt pretensioner deployment, the SDM sends higher frequency pulses to the BCM, which in turn sends a Class 2 message to the ONSTAR module. Upon receiving the Class 2 message, the ONSTAR module transmits a DCO signal to the service center via the vehicle's cellular telephone.

### Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

The measured leakage current to ground is above a specified value in the DCO circuit caused by a short to ground in the DCO circuit.

### Action Taken When the DTC Sets

The SDM turns 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.

• | A history DTC will clear once 255 malfunction free ignition cycles have occurred.

### Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in misdiagnosis, causing a part replacement with reappearance of the malfunction.

The following are possible causes of the malfunction:

• | A short to ground in the DCO circuit

• | The SDM connector

• | The BCM connector C1

• | An internal SDM malfunction

• | An internal BCM malfunction

If an intermittent condition exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

### Test Description

1. Tests to see if the SDM connector is damaged or corroded.

2. Tests to see if the SDM terminals are damaged or corroded.

3. Tests to see if the BCM connector C1 is damaged or corroded.

4. Tests to see if the BCM terminals are damaged or corroded.

5. Tests to see if there is a short to ground in the DCO circuit.

6. Tests to see if the communication status and the units displayed for the DCO circuit are correct.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: SIR Schematics
1 | Did you perform A Diagnostic System Check - SIR? | Go to Step 2 | Go to Diagnostic System Check - SIR
2 |

1. Disconnect the SDM connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
2. Inspect the SDM connector for damage or corrosion that may cause the malfunction. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 3

3 | Inspect the SDM terminals for corrosion or damage that may cause the malfunction. Do the SDM terminals exhibit any sign of damage or corrosion? | Go to Step 9 | Go to Step 4
4 |

1. Disconnect the BCM connector C1. Refer to Body Control Module Replacement in Body Control System.
2. Inspect the BCM connector C1 for damage or corrosion that may cause the malfunction. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 5

5 | Inspect the BCM terminals for corrosion or damage that may cause the malfunction. Do the BCM terminals exhibit any sign of damage or corrosion? | Go to Step 8 | Go to Step 6
6 | Test the DCO circuit for a short to ground. Did you find and correct the condition? | Go to Step 10 | Go to Step 7
7 |

1. Connect the SDM connector.
2. Connect the BCM connector C1.
3. Turn ON the ignition, with the engine OFF.
4. Install a scan tool.
5. With a scan tool, observe the communication status of the ONSTAR test flag in the BCM data list display. Under proper operating conditions, the ONSTAR test flag will display SET.
6. Also, observe the units displayed for the ONSTAR signal. Under proper operating conditions, the ONSTAR will display OK.

Does the scan tool indicate that the ONSTAR test flag displays SET and the ONSTAR signal displays OK?

Go to Step 9

Go to Step 8

8 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 10 | --
9 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you complete the replacement? | Go to Step 10 | --
10 |

1. Reconnect all SIR components.
2. Use a scan tool in order to clear the DTCs.
3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC rest?

Go to Step 2

System OK