GM Service Manual Online
For 1990-2009 cars only

Object Number: 541414  Size: SF
SIR Components
SIR Schematics
SIR Schematic Icons
SIR Schematic Icons

Circuit Description

The driver frontal air bag deployment loop is a 2 wire circuit. One wire is the high side of the loop while the other is the low side of the loop. When you first turn the ignition switch ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Then the SDM performs the following continuous diagnostic tests on the deployment loops:

    • Deployment loop voltage out of range test
    • Deployment loop resistance measurement test

If the voltage out of range test detects a short to voltage condition, the resistance measurement test for that deployment loop will not be performed.

Conditions for Running the DTC

The SDM monitors the driver frontal air bag deployment loop at power on and continuously there after.

Conditions for Setting the DTC

    • If the SDM detects the driver frontal high is greater than 6 volts for 5 consecutive samples, the SDM sets this DTC.
    • Driver frontal high terminal is less than 2.4 volts and driver frontal deployment loop resistance is less than 6 ohms for 5 consecutive samples, the SDM sets this DTC.

The driver frontal deployment loop consists of the following components:

    • Inflatable restraint steering wheel module.
    • Inflatable restraint steering wheel module coil.
    • Harness wiring of driver frontal high and low deployment circuits.
    • Connector terminal contact.

Action Taken When the DTC Sets

    • The SDM sets a DTC.
    • The SDM commands AIR BAG warning lamp ON through a Class 2 message to the cluster (IP).

Conditions for Clearing the DTC

    • Current DTC
       - Driver frontal high is less than or equal to 6 volts for 5 consecutive samples.
       - Driver frontal high terminal is greater than or equal to 2.4 volts and driver frontal deployment loop resistance is less than 6 ohms for 5 consecutive samples
       - CLEAR CODES command
    • History DTC
       - You issue a scan tool CLEAR CODES command.
       - Once 255 malfunctions free ignition cycles have occurred.

Diagnostic Aids

If the DTC is a stored as a history DTC the deployment circuit must be checked for:

    • Frayed insulation
    • Damaged connectors
    • Moisture damage
    • Stretched/broken wires

The fact that the DTC set and now is stored as a history DTC indicates a short to ground or to voltage on either of the two sides of the deployment circuit has happened in the past. The short to ground or voltage will prevent deployment if it happens again during a commanded air bag deployment.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks the driver inflator module in-line connector below the steering wheel restraint module coil.

  2. This step test for the proper operation of inflatable restraint steering wheel module coil and/or inflatable restraint steering wheel inflator module.

  3. This step checks to see if there is a short to ground in the driver frontal high deployment circuit.

  4. This step checks to see if there is a short to ground in the driver frontal low deployment circuit.

  5. This step checks to see if there is a short to voltage in the driver frontal high deployment circuit.

  6. This step determines if there is a short to voltage in the driver frontal low deployment circuit, or if there is a malfunctioning SDM.

  7. This step clears all SIR DTC's.

Step

Action

Value(s)

Yes

No

1

Did you perform the A Diagnostic System Check-SIR?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Turn OFF the ignition.
  2. Disconnect the in-line connector that connects steering wheel restraint module coil to vehicle wiring harness.
  3. Inspect both wiring harness connectors for the following conditions:
  4. • Corrosion
    • Terminal damaged
    • Poor connections/terminal tension

Does connector exhibits any signs of corrosion, terminal damaged, or poor connections?

--

Go to Step 3

Go to Step 4

3

  1. Replace the wiring harness side of in-line connector. Refer to Connector Repairs in Wiring Systems.
  2. If steering wheel restraint module coil exhibits any of the above conditions, the module must be replace. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 18

--

4

  1. Reconnect the in-line connector.
  2. Verify that the connector position assurance (CPA) is properly installed.
  3. Turn ON the ignition, with the engine OFF.
  4. Use the scan tool to request SIR DTCs displayed.

Does the scan tool indicate that this DTC is current?

--

Go to Step 5

Go to Diagnostic Aids

5

  1. Turn OFF the ignition.
  2. Disconnect in-line connector below the steering wheel restraint module coil.
  3. Install the Special Tools SIR Load Tool to vehicle wiring harness in-line connector. Use the appropriate wiring harness connector adaptors where necessary.
  4. Turn ON the ignition, with the engine OFF.
  5. Use the scan tool to request SIR DTCs displayed.

Does the scan tool indicate that this DTC is current?

--

Go to Step 9

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Remove the inflatable restraint steering wheel inflator module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
  3. Disconnect the Special Tools SIR Load Tool from the in-line connector.
  4. Reconnect the in-line connector back together.
  5. Connect the Special Tools SIR Load Tool to the upper inflatable restraint steering wheel module coil connector on the steering column.
  6. Turn ON the ignition, with the engine OFF.
  7. Use the scan tool to request SIR DTCs displayed.

Does the scan tool indicate that this DTC is current?

--

Go to Step 8

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Replace the inflatable restraint steering wheel inflator module. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

8

  1. Turn OFF the ignition.
  2. Replace the inflatable restraint steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 18

--

9

  1. Turn OFF the ignition.
  2. Disconnect the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Disconnect the Fastener Tightening Specifications SIR Load Tool.
  4. Use the DMM and measure the resistance between SDM wiring harness connector driver frontal high circuit and a known good ground.

Does the resistance measure less than the specified value?

OL

Go to Step 10

Go to Step 11

10

Locate and repair a short to ground in the driver frontal high circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

11

Use the DMM and measure the resistance between SDM wiring harness connector driver frontal low circuit and a known good ground.

Does the resistance measure less than the specified value?

OL

Go to Step 12

Go to Step 13

12

Locate and repair a short to ground in the driver frontal low circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

13

  1. Turn ON the ignition, with the engine OFF.
  2. Use the and measure the voltage between SDM wiring harness connector driver frontal high circuit and a known good ground.

Does the voltage measured less than the specified value?

1 V

Go to Step 15

Go to Step 14

14

Locate and repair a short to voltage in the driver frontal high circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

15

Use the DMM and measure the voltage between SDM wiring harness connector driver frontal low circuit and a known good ground.

Does the voltage measured less than the specified value?

1 V

Go to Step 17

Go to Step 16

16

Locate and repair a short to voltage in the driver frontal low circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

17

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

Did you complete the replacement?

--

Go to Step 18

--

18

  1. Reconnect all SIR components.
  2. Verify that all components, connectors and CPAs are properly mounted.
  3. Turn ON the ignition, with the engine OFF.
  4. Use the scan tool in order to Clear the DTCs.
  5. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Did you complete the action?

--

Go to Diagnostic System Check - SIR

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