GM Service Manual Online
For 1990-2009 cars only

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.

These test 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.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

DTC B1409 LF Side Impact Sensor Invalid Serial Data Received

Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

Conditions for Setting the DTC

A communication error occurs between the SDM and the driver side impact sensor.

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

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section.

Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section.

1

Did you perform a Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Confirm the ignition switch is OFF and the sensing and diagnostic module (SDM) has been removed.
  2. Wait for 1 minute for the SDM charger to be discharged.

Has the SDM discharged?

Go to Step 3

--

3

Visually inspect any damage for the driver side impact sensor wiring.

Is the driver side impact sensor wiring damaged?

Go to Step 4

Go to Step 5

4

Replace the air bag wiring.

Is the replacement complete?

Go to Step 7

--

5

  1. Replace the driver side impact sensor. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  2. Confirm the ignition switch is ON.
  3. Use the scan tool in order to clear the DTCs.
  4. Perform the Diagnostic System Check - Vehicle .

Is the DTC removed?

Go to Step 7

Go to Step 6

6

Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Is the replacement complete?

Go to Step 7

--

7

  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