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 tests to diagnose critical malfunctions within the SDM itself.

After passing these tests, ignition and deployment loop voltages are measured to ensure that they are within their respective normal voltage ranges. The SDM then proceeds with the resistance measurement test.

Each inflator low terminal is grounded through a current sink, and each inflator current source is connected to each inflator high terminal to allow a known amount of current to flow.

By monitoring the voltage difference between each inflator high and low, the SDM calculates the combined resistance of the inflator module, the wiring harness and the connector terminal contacts.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B0022 Driver Frontal Deployment Loop Resistance Low
    • DTC B0024 Driver Frontal Deployment Loop Voltage Out of Range
    • DTC B0026 Driver Frontal Deployment Loop Open

Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

Conditions for Setting the DTC

B0022

DTC B0022 will set when the SDM detects the resistance of steering wheel module deployment loop is lower than 1.8 ohms.

B0024

DTC B0024 will set when the SDM detects the resistance of steering wheel module high is greater than 7.5 volts for 5 consecutive test cycles, or voltage at the steering wheel module high is less than 1.5 volts and resistance of the steering wheel module deployment loop is less than 6 ohms for 5 consecutive test cycles.

B0026

DTC B0026 will set when the SDM detects the resistance of steering wheel module deployment loop is higher than 4.5 ohms for 500 milliseconds, or voltage at the steering wheel module high is less than 2 volts and resistance of the steering wheel module deployment loop is 4.5 or more ohms for 500 milliseconds.

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.

Diagnostic Aids

B0022

An intermittent condition is likely to be caused by a short between the steering wheel module high and low circuits.

B0024

An intermittent condition is likely to be caused by a short to ground or voltage in the steering wheel module high and low circuits.

B0026

An intermittent condition is likely to be caused by a poor connection at the steering wheel module connector or SDM.

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

Is DTC B0022, B0024, or B0026 set as a current DTC?

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn the ignition OFF.
  2. Wait 1 minute for the sensing and diagnostic module (SDM) capacitor to discharge.
  3. Examine the wiring and the connector at the steering wheel module.

Is the connector disconnected or wiring damaged?

Go to Step 4

Go to Step 5

4

Connect the steering wheel module connector or replace the wiring.

Is the repair complete?

Go to Step 11

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5

  1. Turn the ignition OFF.
  2. Disconnect the connector for the steering wheel module.
  3. Disconnect the steering wheel module coil connector.
  4. If DTC B0022 is present, test for a short between the steering wheel module high and the steering wheel module low circuits.
  5. If DTC B0024 is present, test the steering wheel module high and the steering wheel module low circuits for a short to ground or short to voltage.
  6. If DTC B0026 is present, test the steering wheel module high and the steering wheel module low circuits for an open or high resistance.
  7. For all the above conditions, refer to Circuit Testing and Wiring Repairs .

Did you find the condition?

Go to Step 10

Go to Step 6

6

  1. Turn the ignition OFF.
  2. Disconnect the connector for the steering wheel module coil.
  3. Disconnect the connector at the SDM.
  4. If DTC B0022 is present, test for a short between the steering wheel module high and the steering wheel module low circuits at the steering wheel module coil connector.
  5. If DTC B0024 is present, test the steering wheel module high and the steering wheel module low circuits for a short to ground or short to voltage at the steering wheel module coil connector.
  6. If DTC B0026 is present, test the steering wheel module high and the steering wheel module low circuits for an open or high resistance at the steering wheel module coil connector.
  7. For all the above conditions, refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

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

Did you complete the replacement?

Go to Step 8

--

8

  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 9

System OK

9

Replace the steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Did you complete the replacement?

Go to Step 11

--

10

Replace the steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

Go to Step 11

--

11

  1. Reconnect all SIR components.
  2. Verify that all components, connectors and 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

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