GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The sensing and diagnostic module (SDM) contains a sensing device which converts vehicle velocity changes to an electrical signal. The electrical signal generated is processed by the SDM and then compared to a value stored in memory. When the generated signal exceeds the stored value, additional signal processing is performed and the generated signals are compared to signals stored in memory. When two of the generated signals exceed the stored values, the SDM will cause sufficient current to flow through the inflator modules to deploy the air bags and cause DTC B0051 to be set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0051 Deployment Commanded

Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The SDM detects a frontal crash within 30 degrees of the centerline of the vehicle, of sufficient force to warrant deployment of the air bags.

Action Taken When The DTC Sets

The SDM commands the AIR BAG indicator ON and records crash data.

Conditions for Clearing the DTC

The SDM is replaced.

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 the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn the ignition to LOCK and remove the key.
  2. Check for deployed air bags.

Have the air bags deployed?

Go to Step 3

Go to Step 4

3

  1. Remove the airbag fuse.
  2. Turn the steering wheel so the front wheels are pointing straight ahead.
  3. Perform inspections and component replacement. Refer to Repairs and Inspections Required After a Collision .
  4. Replace the sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the replacement?

Go to Step 6

--

4

Inspect the front of the vehicle and undercarriage for signs of impact.

Are there any signs of impact?

Go to Step 3

Go to Step 5

5

  1. Turn the ignition to LOCK and remove the key.
  2. Disconnect the instrument panel (I/P) module and the steering wheel module coil connector on the steering column.
  3. Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the replacement?

Go to Step 6

--

6

  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