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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 2WD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Air Bag Indicator Circuit Malfunction

Circuit Description

The AIR BAG warning lamp is controlled by the inflatable restraint sensing and diagnostic module (SDM) via class 2 serial data. When the ignition switch is first turned to the RUN position, the SDM performs tests to diagnose critical malfunctions within itself. The SDM then commands the AIR BAG warning lamp OFF after it has flashed 7 times.

Diagnostic Aids
    •  If ignition 1 voltage is outside of the normal operating voltage range (9-16 volts), the AIR BAG warning lamp will come ON solid with no DTCs set.
    • The loss of serial data communication between the SDM and the instrument panel cluster (IPC), will cause the AIR BAG warning lamp to come ON solid. Refer to DTC U1001-U1254 in Computer/Integrating Systems.

Test Description

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

  1. This step checks to see if the AIR BAG warning lamp flashes 7 times when the ignition switch is first turned to the RUN position.

    2.

  2. This step checks to see if DTC U1088 is present in the instrument panel cluster (IPC).

    3.

  3. This step checks to see if the AIR BAG warning lamp can be commanded ON.

    4.

  4. This step checks to see if ignition 1 voltage to the SDM is more than 9 volts.

    5.

  5. This step determines if ignition 1 voltage to the SDM is more than 16 volts or if there is a malfunctioning SDM.

    6.

  6. This step inspects the SDM wiring harness connector for corrosion or damage.

    7.

  7. This step tests for an open or high resistance in the ignition 1 voltage circuit between the SDM and the SIR fuse.

    8.

  8. This step tests for an open or high resistance in the ignition 1 voltage circuit to the SIR fuse.

    9.

  9. This step tests for an open or high resistance in the SDM ground circuit or if there is a malfunctioning SDM.

Step

Action

Value(s)

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn OFF the ignition.
  2. Observe the AIR BAG warning lamp while turning the ignition switch to the RUN position.

Does the AIR BAG warning lamp flash 7 times?

--

Go to Step 3

Go to Step 16

3

  1. Install a scan tool.
  2. Establish communication with the instrument cluster.
  3. Use the scan tool to request the instrument cluster DTC display.

Does the scan tool indicate that DTC U1088 is current?

--

Go To DTC U1001-U1254 in Computer/Integrating Systems

Go to Step 4

4

Use the scan tool to command the AIR BAG warning lamp ON.

Does the AIR BAG warning lamp command ON?

--

Go to Step 5

Go to Step 16

5

  1. Establish communication with the inflatable restraint sensing and diagnostic module (SDM).
  2. Use the scan tool to request the SIR DTC display.

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

9 V

Go to Step 6

Go to Step 7

6

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

16 V

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 15

7

  1. Turn OFF the ignition.
  2. Disconnect the SDM wiring harness connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Inspect the SDM wiring harness connector for signs of corrosion or damage.

Does the connector exhibit any signs of corrosion or damage?

--

Go to Step 8

Go to Step 9

8

Repair or replace the SDM wiring harness connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the replacement?

--

Go to Step 17

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9

  1. Disable the SIR system. Refer to SIR Disabling and Enabling .
  2. Use the DMM in order to measure the resistance between the SDM wiring harness connector ignition 1 circuit and the output side of the SIR fuse. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure within the specified value?

0-2 ohms

Go to Step 11

Go to Step 10

10

Locate and repair an open or high resistance in the ignition 1 circuit between the SIR fuse and the SDM wiring harness connector. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 17

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11

  1. Turn ON the ignition, with the engine OFF.
  2. Use the DMM in order to measure the voltage between the power feed to the SIR fuse and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the voltage measure near the specified value?

12 V

Go to Step 13

Go to Step 12

12

Locate and repair an open or high resistance in the power feed circuit to the SIR fuse. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 17

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13

Use the DMM in order to measure the resistance of the SDM ground circuit between the SDM wiring harness connector and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure less than the specified value?

2 ohms

Go to Step 15

Go to Step 14

14

Locate and repair an open or high resistance in the SDM ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 17

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15

Replace the SDM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 17

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16

Replace the instrument cluster. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 17

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17
  1. Reconnect all SIR and instrument cluster system components.
  2. Verify that all components, connectors, and connector position assurances (CPAs) are properly mounted.

Have all SIR and instrument cluster components been properly connected and mounted?

--

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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