GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 GTO 🢒 Restraints 🢒 SIR 🢒 Air Bag Indicator Always On

Circuit Description

The ignition switch supplies battery voltage to the AIR BAG indicator using the instrument panel fuse. The AIR BAG indicator is controlled by the sensing and diagnostic module (SDM) via universal asynchronous receiver transmitter (UART) data. When the ignition switch is first turned to the ON position, the SDM responds by illuminating the AIR BAG indicator for approximately 6 seconds while performing diagnostic tests on the SIR system.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • An open or high resistance in serial data line
    • A misconstrued instrument cluster
    • Battery voltage below 8 volts or above 21.2 volts
    • Seat belt pretensioners have deployed
    • SDM has deployed
    • SDM does not receive a poll from the body control module (BCM)
    • An open or high resistance in the SDM ground circuit
    • A open, high resistance or short to ground in the SDM ignition voltage circuit
    • An internal SDM malfunction
    • An internal BCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for serial data communication between the SDM and the scan tool.

    2.

  2. This step tests for proper instrument panel cluster (IPC) configuration.

    3.

  3. This step tests for communication with other modules.

    4.

  4. This step tests for a deployed SDM.

    5.

  5. This step tests the SDM ignition voltage circuit.

    6.

  6. This step tests the SDM ignition voltage (after 3 seconds).

    7.

  7. This step tests for a battery malfunction.

    8.

  8. This step tests for a charging system malfunction.

    9.

  9. This step tests the SDM ignition voltage circuit.

    10.

  10. This step tests the SDM ground circuit.

    11.

  11. This step tests the SDM serial data line to the IPC.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform a Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Air Bag indicator.

Does the Air Bag indicator remain illuminated after 6 seconds?

Go to Step 3

Go to Diagnostic Aids

3

  1. Use the scan tool to request the ID information display.
  2. With the scan tool, observe the ID information.

Does the ID information display?

Go to Step 4

Go to Step 6

4
  1. Use the scan tool to request the SIR data list display.
  2. With the scan tool, observe the BCM Poll in the SIR data list.

Has the sensing and diagnostic module (SDM) received a body control module (BCM) poll?

Go to Step 5

Go to Step 6

5

  1. Use the scan tool to request the SIR data list display.
  2. With the scan tool, observe the SIR Serial communication in the SIR data list.

Is the instrument cluster configured to the SIR system?

Go to Step 7

Go to Diagnostic Starting Point - Instrument Panel, Gages and Console

6

Using the scan tool, establish communication with the BCM and the powertrain control module (PCM).

Did the scan tool establish communication with the BCM and PCM?

Go to Step 8

Go to Scan Tool Does Not Communicate with GMLAN Device

7

  1. Use the scan tool to request the SIR data list display.
  2. With the scan tool, observe the Airbag Deployment Commanded in the SIR data list.

Does the display indicate the module has deployed?

Go to Repairs and Inspections Required After a Collision

Go to Step 9

8

  1. Disconnect the sensing and diagnostic module (SDM) connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Using EL-46863 Test Leads, check the voltage between the SDM ignition voltage circuit and a known good ground.

    4. Refer to Circuit Testing .

Is battery voltage present?

Go to Step 14

Go to Step 17

9

  1. Use the scan tool to request the SIR data list display.
  2. With the scan tool, observe the Battery State in the SIR data list.

Is Battery State displayed as Okay?

Go to Step 10

Go to Step 11

10
  1. Perform Diagnostic System Check - Vehicle. Refer to Diagnostic System Check - Vehicle .
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the Air Bag indicator.

Does the Air Bag indicator remain illuminated after 6 seconds?

Go to Step 20

Go to Step 21

11

Check the battery. Refer to Battery Inspection/Test .

Did you find and correct the condition?

Go to Step 21

Go to Step 12

12

Check the Charging System. Refer to Battery Charging .

Did you find and correct the condition?

Go to Step 21

Go to Step 13

13

  1. Disconnect the SDM connector.
  2. Operate the engine at 2,500 RPM with the headlamps ON.
  3. Using EL-46863 , check the voltage between the SDM ignition voltage circuit and a known good ground. Refer to Circuit Testing .

Does voltage measure approximately the same as during the charging system tests?

Go to Step 14

Go to Step 17

14
  1. Turn OFF the ignition.
  2. Disconnect the SDM connector.
  3. Inspect the SDM connector for the following conditions:
    4. • Corrosion
    • Damaged terminals
    • Poor connections/terminal tension

Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 21

Go to Step 15

15

  1. Turn OFF the ignition.
  2. Disconnect the SDM connector.
  3. Using EL-46863 , check for continuity between the SDM ground circuit and a known good ground. Refer to Circuit Testing .

Does continuity exist?

Go to Step 16

Go to Step 18

16

  1. Turn OFF the ignition.
  2. Disconnect the SDM connector.
  3. Using EL-46863 , check the serial data line for continuity between the SDM and the instrument panel cluster (IPC). Refer to Circuit Testing .

Does continuity exist?

Go to Step 20

Go to Step 19

17

Repair an open, high resistance, or a short to ground in the SDM ignition voltage circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 21

--

18

Repair an open or high resistance in the SDM ground circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 21

--

19

Repair an open or high resistance in the SDM serial data line to IPC. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 21

--

20

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

Did you complete the replacement?

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2