GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Spark 🢒 Restraints 🢒 SIR 🢒 DTC 021

Circuit Description

When the ignition switch is turned ON, the sensing and diagnostic module (SDM) will perform tests to diagnose any malfunctions within itself.

After passing these tests, the SDM will check the passenger air bag and the passenger circuit. The SDM allows a very small amount of current to flow through the circuit. The SDM monitors the circuit resistance during this check.

Conditions for Setting the DTC

Connection between the passenger firing circuit and the passenger pretensioner circuit or SDM internal connection problem may exist.

Step

Action

Values

Yes

No

Caution: Refer to Battery Disconnect Caution in the Preface section.

Caution: Refer to SIR Special Tool Caution in the Preface section.

 

1
  1. Disconnect the negative battery cable.
  2. Wait 1 minute for the SDM capacitor to discharge.
  3. Examine the wiring and the connector at the passenger side air bag module and the passenger pretensioner module.

Is the connector disconnected?

--

Go to Step 2

Go to Step 3

2
  1. Reconnect the passenger side air bag module and the passenger pretensioner module connector.
  2. Reconnect the negative battery cable.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

3
  1. Disconnect the electrical connector for the passenger side air bag module and the passenger 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 passenger air bag module and the passenger pretensioner module.

  3. Connect an ohmmeter to the terminals on the SDM side of the wiring harness connector for the passenger pretensioner module. Refer to Diagnostic Illustration 19 in SIR Diagnostic Illustrations .

Does the ohmmeter show the specified value?

0 ohms

Go to Step 4

Go to Step 6

4
  1. Replace the SDM.
  2. Reconnect the negative battery cable.
  3. Set the scan tool for CODE ERASE.
  4. Perform the diagnostic system check.

Does DTC 021 still show as a current fault?

--

Go to Step 5

System OK

5
  1. Replace the passenger pretensioner module.
  2. Reconnect the negative battery cable.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

6
  1. Replace the supplemental inflatable restraints (SIR) wiring harness.
  2. Reconnect the negative battery cable.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--