GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy C Silverado - 2WD 🢒 Restraints 🢒 SIR 🢒 AIR BAG Warning Lamp Comes On Steady

Object Number: 618280 Size: SF
SIR Components
SIR Schematics
SIR Schematic Icons
SIR Schematic Icons

Circuit Description

When the ignition switch is first turned to RUN, the IGN 1 Fuse applies battery voltage to the AIR BAG warning lamp that is connected to AIR BAG INDICATOR CONTROL, terminal 7. The AIR BAG Fuse applies battery voltage to the Ignition Positive Voltage input, terminal 10. The inflatable restraint sensing and diagnostic module (SDM) responds by flashing the AIR BAG warning lamp 7 times. If Ignition Positive Voltage is outside of the normal operating voltage range (8.2 volts - 17.1 volts), the AIR BAG warning lamp will come ON solid with no DTCs set.

Diagnostic Aids

In order to disable the shorting bar from terminal 6 to terminal 7 inside the inflatable restraint sensing and diagnostic module (SDM) harness connector, the following 2 conditions must be met:

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

When measurements are requested in this table, use the J 39200 DMM with the correct terminal adapter from the J 35616 Connector Test Adapter Kit. When an inspection for proper connection is requested, refer to Testing for Electrical Intermittents in Wiring Systems. When a wire, connector or terminal repair is requested, use the J-38125 Terminal Repair Kit and refer to Wiring Repairs in Wiring Systems.

Test Description

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

  1. This test checks for sufficient Ignition Positive Voltage applied to the SDM.

    2.

  2. This test checks for excessive Ignition Positive Voltage applied to the SDM.

    3.

  3. This test checks for a properly installed CPA.

    4.

  4. This test determines if the SDM is turning on the AIR BAG warning lamp.

    5.

  5. This test checks for a damaged shorting bar.

    6.

  6. This test determines whether the malfunction is a short to ground in CKT 358.

    7.

  7. This test checks for a short between CKTs 358 and 1851.

    8.

  8. This step checks to see if the AIR BAG Fuse is OK. An open AIR BAG Fuse would cause the AIR BAG warning lamp to come on steady.

    9.

  9. This test checks whether a short to ground caused the AIR BAG Fuse to open.

    10.

  10. This test determines whether the short to ground is due to a short in the wiring or internal to the SDM.

    11.

  11. This test determines whether the short to ground is due to a short in the wiring or internal to the inflatable restraint IP module switch.

    12.

  12. This test checks for a disconnected SDM.

    13.

  13. This test checks for an open in the Igntion Positive Voltage circuit.

AIR BAG Warning Lamp Comes On Steady

Step

Action

Value(s)

Yes

No

1

Was the SIR Diagnostic System Check performed?

--

Go to Step 2

Go to SIR Diagnostic System Check

2

  1. Turn the ignition switch to the OFF position.
  2. Connect the Scan Tool to the data link connector (DLC).
  3. Turn the ignition switch to the RUN position.
  4. Request the SIR data list display.

Is Ignition Positive Voltage more than the specified value?

8.2 V

Go to Step 3

Go to Step 14

3

  1. Set the parking brake.
  2. Start the engine.
  3. Using the Scan Tool , read the SIR data list.

Is Ignition Positive Voltage more than the specified value?

17.1 V

Go to Charging System Check in Engine Electrical

Go to Step 4

4

  1. Turn the ignition switch to the OFF position.
  2. Inspect the SDM harness connector CPA.

Is the CPA properly installed?

--

Go to Step 6

Go to Step 5

5

Properly install the CPA.

Is the repair complete?

--

Go to SIR Diagnostic System Check

--

6

  1. Disconnect the inflatable restraint steering wheel and IP module yellow 2-way connectors located near the base of the steering column and behind the glove box.
  2. Disconnect the SDM harness connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Install J 38715-96 SIR Shorting Bar Tool within the SDM harness connector.
  4. Install the CPA.
  5. Turn the ignition switch to the RUN position.

Does the AIR BAG warning lamp come ON steady?

--

Go to Step 7

Go to Sensing and Diagnostic Module Integrity Check

7

  1. Turn the ignition switch to the OFF position.
  2. Remove J 38715-96 from the SDM harness connector.
  3. Inspect the shorting bar within the SDM harness connector.

Is the shorting bar damaged or corroded?

--

Go to Step 8

Go to Step 9

8

Replace the SDM harness connector.

Is the repair complete?

--

Go to Step 30

--

9

  1. Install J 38715-96 within the SDM harness connector.
  2. Install the CPA.
  3. Disconnect the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.
  4. Measure the resistance from the SDM harness connector terminal 7 to ground.

Is the resistance reading less than the specified value?

OL

Go to Step 10

Go to Step 13

10

  1. Disconnect CKT 1851 from ground. Refer to SIR Components .
  2. Measure the resistance from the SDM harness connector terminal 7 to terminal 6.

Is the resistance reading less than the specified value?

OL

Go to Step 12

Go to Step 11

11

Repair a short to ground condition in CKT 358.

Is the repair complete?

--

Go to Step 30

--

12
  1. Repair the short between CKTs 358 and 1851.
  2. Inspect CKT 1851 for any cutting or chaffing.

Is the repair complete?

--

Go to Step 30

--

13

Service the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Is the repair complete?

--

Go to Step 30

--

14

  1. Turn the ignition switch to the OFF position.
  2. Remove the AIR BAG Fuse.
  3. Inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 22

Go to Step 15

15

  1. Replace the AIR BAG Fuse.
  2. Turn the ignition switch to the RUN position for 10 seconds.
  3. Turn the ignition switch to the OFF position.
  4. Remove the AIR BAG Fuse.
  5. Inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 21

Go to Step 16

16

  1. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  2. Measure the resistance between the output side of the AIR BAG Fuse, terminal A5 and a known good ground.

Is the measured resistance less than the specified value?

OL

Go to Step 17

Go to Step 27

17

Does this vehicle have a inflatable restraint IP module switch?

--

Go to Step 18

Go to Step 20

18

  1. Disconnect the inflatable restraint IP module switch. Refer to Inflatable Restraint Instrument Panel Module Disable Switch Replacement .
  2. Replace the AIR BAG Fuse.
  3. Turn the ignition switch to the RUN position, wait 10 seconds, then turn the ignition switch Off.
  4. Remove and inspect the AIR BAG Fuse.

Is the AIR BAG Fuse good?

--

Go to Step 19

Go to Step 20

19
  1. Replace the inflatable restraint IP module switch. Refer to Inflatable Restraint Instrument Panel Module Disable Switch Replacement .
  2. Install the AIR BAG Fuse.

Has the inflatable restraint IP switch been replaced and the AIR BAG Fuse installed?

--

Go to Step 30

--

20
  1. Repair a short to ground condition in CKT 1139.
  2. Connect the SDM.
  3. Replace the AIR BAG Fuse.

Is the repair complete?

--

Go to Step 30

--

21

Install the AIR BAG Fuse.

Is the repair complete?

--

Go to Step 30

--

22

Inspect the SDM harness connector.

Is the connector securely connected to the SDM?

--

Go to Step 24

Go to Step 23

23
  1. Properly connect the SDM harness connector.
  2. Install the CPA.

Is the repair complete?

--

Go to Step 30

--

24
  1. Disconnect the inflatable restraint steering wheel and IP module yellow 2-way connectors located neat the base of the steering column and behind the glove box.
  2. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Inspect for proper connection to the SDM at terminal 10.

Is the SDM harness connector terminal damaged or corroded?

--

Go to Step 25

Go to Step 26

25

Replace the SDM harness connector. Refer to Wiring Repair .

Is the repair complete?

--

Go to Step 30

--

26

Inspect the SDM terminals for damage or corrosion.

Are any terminals damaged or corroded?

--

Go to Step 27

Go to Step 28

27

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

Is the repair complete?

--

Go to Step 30

--

28

Measure the resistance from the SDM harness connector terminal 10 to each terminal of the AIR BAG Fuse fuseholder.

Is either resistance reading within the specified values?

0-5 ohms

Go to Sensing and Diagnostic Module Integrity Check

Go to Step 29

29

Repair an open condition in CKT 1139.

Is the repair complete?

--

Go to Step 30

--

30
  1. Reconnect all the SIR system components.
  2. Ensure that all of the components are properly mounted.

Have all the SIR components been reconnected and properly mounted?

--

Go to SIR Diagnostic System Check

--