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 resistances. If the resistance is in the 2 kilo ohms between 10 kilo ohms, the defect may occur depending upon the SDM. The normal resistance is over 10 kilo ohms.

Conditions for Setting the DTC

    • The belt pretensioner wiring of driver high is shorted to battery wiring.
    • The belt pretensioner wiring of driver low is shorted to battery wiring.

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

  1. Disconnect the battery negative cable.
  2. Wait 1 minute for the sensing and diagnostic module (SDM) capacitor to discharge.
  3. The capacitor supplies reserve power to deploy the driver seat belt pretensioner even if the battery has been disconnected.

  4. Visually inspect the supplemental inflatable restraint (SIR) wiring harness.

Is there any visible damage to the SIR wiring harness?

--

Go to Step 3

Go to Step 4

3

  1. Replace the SIR wiring harness.
  2. Reconnect the negative battery cable.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

4

  1. Disconnect the electrical connector for the driver seat belt pretensioner module.
  2. Disconnect the electrical connector at the SDM.
  3. The shorting bar at the disconnected SDM connector will create a complete circuit between the wires from the driver seat belt pretensioner module.

  4. Use a multimeter to measure the voltage at one of the terminals on the SDM side of the SIR wiring harness connector for the driver seat belt pretensioner module.

Is the voltage greater than the specified value?

0 V

Go to Step 3

Go to Step 5

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 012 still shown as a current fault?

--

Go to Step 6

System OK

6

  1. Replace the driver seat belt pretensioner module.
  2. Reconnect the negative battery cable.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--