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.

The 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 deploy loops. The SDM inspects the wiring connection to the passenger air bag module by letting the infinitesimal current flow through the internal circuit and verify the resistance.

Conditions for Setting the DTC

The resistance of the passenger side air bag deployment loop is over 2.8 ohms.

Step

Action

Values

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.

 

1

Perform the Diagnostic System Check - SIR.

Is the Diagnostic System Check - SIR complete?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

Visually inspect any damage for the passenger side air bag wiring and the connector.

Is the air bag wiring damaged or the connector disconnected?

--

Go to Step 3

Go to Step 4

3

Repair the wiring damage or connect the connector.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

4

  1. Confirm the ignition switch is OFF.
  2. Disconnect the connector of the passenger side air bag module.
  3. Remove the connector of the sensing and diagnostic module (SDM).
  4. Measure the resistance between the terminal 1, 2 passenger side air bag module and the terminal 16, 17 of the SDM.

Is the resistance at the specified value?

10 K ohms

Go to Step 5

Go to Step 7

5

  1. Replace the SDM.
  2. Reconnect the negative battery cable.
  3. Set the scan tool to CODE ERASE.
  4. Perform the Diagnostic System Check - SIR.

Is DTC 056 still shown as a current fault?

--

Go to Step 6

Go to Diagnostic System Check - SIR

6

Replace the passenger side air bag module.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

7

Replace the air bag wiring.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--