GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 2WD 🢒 Body and Accessories 🢒 Instrument Panel, Gages, and Console 🢒 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 seven 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 inflatable restraint sensing and diagnostic module (SDM) and the instrument panel cluster (IPC), will cause the AIR BAG warning lamp to come ON solid. Refer to DTC U1000 and U1255 in Data Link Communications.

Test Description

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

  1. This step checks to see if the AIR BAG warning lamp flashes seven 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 V.

    5.

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

    6.

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

    7.

  7. Tests for an open or high resistance in the ignition 1 voltage circuit between the SDM and the AIR BAG Fuse.

    8.

  8. Tests for an open or high resistance in the ignition 1 voltage circuit to the AIR BAG Fuse.

    9.

  9. 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 SIR Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

Did you perform the Instrument Cluster Diagnostic System Check?

--

Go to Step 3

Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages and Console

3

  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 seven times?

--

Go to Step 4

Go to Step 17

4

  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 U1000 and U1255 in Data Link Communications

Go to Step 5

5

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

Does the AIR BAG warning lamp command ON?

--

Go to Step 6

Go to Step 17

6

  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 7

Go to Step 8

7

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

16 V

Go to Diagnostic System Check - Engine Electrical in Engine Electrical

Go to Step 16

8

  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. 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 9

Go to Step 10

9

Repair or replace the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the replacement?

--

Go to Step 18

--

10

  1. Disable the SIR system. Refer to Disabling the SIR System .
  2. UsingJ 39200 DMM measure the resistance between the inflatable restraint sensing and diagnostic module (SDM) wiring harness connector ignition 1 circuit and the output side of the AIR BAG Fuse. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure within the specified value?

0-2 ohms

Go to Step 12

Go to Step 11

11

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

Did you complete the repair?

--

Go to Step 18

--

12

  1. Turn ON the ignition, with the engine OFF.
  2. UsingJ 39200 DMM measure the voltage between the power feed to the AIR BAG 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 14

Go to Step 13

13

Locate and repair an open or high resistance in the power feed circuit to the AIR BAG Fuse. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

14

UsingJ 39200 DMM measure the resistance of the inflatable restraint sensing and diagnostic module (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 16

Go to Step 15

15

Locate and repair an open or high resistance in the inflatable restraint sensing and diagnostic module (SDM) ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

--

16

Replace the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

17

Replace the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages and Console.

Did you complete the replacement?

--

Go to Step 18

--

18
  1. Reconnect all SIR and Instrument Cluster system components.
  2. Verify that all components, connectors, and CPAs are properly mounted.

Have all SIR and Instrument Cluster components been properly connected and mounted?

--

Go to Diagnostic System Check - SIR

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