GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Air Bag Indicator Always On

Circuit Description

The AIR BAG indicator is controlled by the inflatable restraint sensing and diagnostic module (SDM). When the ignition is turned ON, the SDM performs tests to diagnose critical malfunctions within itself. The SDM then commands the AIR BAG indicator OFF after it has flashed seven times. If a malfunction is detected, the AIR BAG indicator will be turned ON solid.

Diagnostic Aids
    • If ignition 1 voltage is outside of the normal operating range (9 -16 volts), the AIR BAG indicator will come ON solid with no DTCs set.
    • A broken or chafed wire in the AIR BAG indicator control circuit may cause an intermittent condition to occur. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. This step checks to see if Ignition 1 voltage to the SDM is more than 9 V.

    2.

  2. This step checks to see if Ignition 1 voltage to the SDM is more than 16 V.

    3.

  3. Tests for a short to ground in the AIR BAG indicator control circuit.

    4.

  4. Inspects for poor connections at the SDM harness connector.

    5.

  5. Inspects for poor connections at the instrument panel cluster (IPC) harness connector.

    6.

  6. Tests for an open or high resistance in the Ignition 1 circuit between the SDM and the fuse block.

    7.

  7. Tests for an open or high resistance in the Ignition 1 voltage circuit that feeds the AIR BAG Fuse.

    8.

  8. Tests for and open or high resistance in the SDM ground circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: SIR Schematics

1

Did you perform A Diagnostic System Check - SIR?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the ignition 1 voltage parameter in the SIR data list

Does the ignition 1 voltage displayed measure more than the specified value?

9 V

Go to Step 3

Go to Step 8

3

Does the ignition 1 voltage displayed measure more than the specified value?

16 V

Go to Diagnostic System Check - Engine Electrical in Engine Electrical

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Turn ON the ignition, with the engine OFF.

Does the AIR BAG indicator remain illuminated?

--

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition.
  2. Test the AIR BAG indicator control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 7

6

  1. Turn OFF the ignition.
  2. Inspect the SDM connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

7

Inspect the IPC connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

8

  1. Disable the SIR system. Refer to Disabling the SIR System .
  2. Test the ignition 1 circuit between the SDM and the fuse block for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 9

9

Test the ignition 1 circuit that feeds the AIR BAG Fuse for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

10

Test the SDM ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

11

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

Did you complete the replacement?

--

Go to Step 13

--

12

Repair or replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Did you complete the repair?

--

Go to Step 13

--

13
  1. Reconnect all SIR and Instrument Cluster system components.
  2. Verify that all components, connectors and CPAs are properly mounted.

Have all SIR and IPC components been reconnected and properly mounted?

--

Go to Diagnostic System Check - SIR

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