GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The ignition switch supplies ignition 1 voltage to the inflatable restraint sensing and diagnostic module (SDM) using the F1 fuse. The ignition switch also supplies battery voltage to the AIR BAG indicator using the F4 fuse. The AIR BAG indicator is connected to the AIR BAG indicator output of the SDM. When the ignition switch is first turned to the ON position, the SDM responds by flashing the AIR BAG indicator seven times.

Diagnostic Aids

In order to disable the shorting bar between the air bag indicator control circuit and ground inside the SDM wiring harness connector, the following two conditions must be met:

    • The SDM wiring harness connector must be properly connected to the SDM.
    • The connector position assurance (CPA) must be properly installed in the SDM wiring harness connector.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines if the malfunction is caused by a battery overcharge condition.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: Component Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn OFF the ignition.
  2. Disconnect the sensing and diagnostic module (SDM) connector.
  3. Inspect the SDM connector and the shorting bar for damage or corrosion.

Did you find and correct the condition?

Go to Step 5

Go to Step 3

3

Test the air bag indicator control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

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

Did you complete the replacement?

Go to Step 5

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5

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2