GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy C Silverado - 2WD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 SIR Diagnostic System Check

Caution: In order to avoid deploying the air bag when troubleshooting the SIR system, use only the equipment specified in this manual and the instructions given in this manual. Failure to use the specified equipment as instructed could cause air bag deployment, personal injury to you or someone else, or unnecessary SIR system repairs.

Caution: If any water enters the vehicle's interior up to the level of the carpet or higher and soaks the carpet, the sensing and diagnostic module (SDM) and the SDM harness connector may need to be replaced. The SDM could be activated when powered, which could cause deployment of the air bag(s) and result in personal injury. Before attempting these procedures, the SIR system must be disabled. Refer to Disabling the SIR System.

With the ignition OFF, inspect the SDM mounting area, including the carpet. If any significant soaking or evidence of significant soaking is detected, you must perform the following tasks:

  1. Remove all water.
  2. Repair the water damage.
  3. Replace the SDM harness connector.
  4. Replace the SDM.
Failure to follow these tasks could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs.

These diagnostic procedures will help you to find and repair SIR system malfunctions. This service category also contains information for repairing SIR system malfunctions. For best results, use the diagnostic tables, and follow the sequence listed below:

  1. Perform the SIR Diagnostic System Check. All SIR diagnostics must begin with the SIR Diagnostic System Check. The SIR Diagnostic System Check determines the following results:
    2. • Proper AIR BAG warning lamp operation
    • Ability of the SDM to communicate through the data link connector (DLC)
    • Existence of SIR diagnostic trouble codes (DTC)
  2. Refer to the diagnostic table as directed by the SIR Diagnostic System Check. The diagnostic tables will help enable you to diagnose any SIR system malfunction. Bypassing these procedures may result in the following problems:
    3. • Extended diagnostic time
    • Incorrect diagnosis
    • Incorrect parts replacement
  3. Repeat the SIR Diagnostic System Check after you perform any repair or diagnostic procedures. This will verify that you correctly performed the repair. This will also ensure that no other malfunctions exist.

Circuit Description

The ignition switch supplies Ignition Positive Voltage to the inflatable restraint sensing and diagnostic module (SDM) at terminal 10 using the AIR BAG Fuse. When the ignition switch is first turned to the RUN position, the SDM responds by flashing the AIR BAG warning lamp 7 times, then turning the AIR BAG warning lamp OFF, while performing tests on the SIR system.

Diagnostic Aids

You must diagnose the diagnostic trouble codes in the order specified by the SIR Diagnostic System Check. Failure to do so may result in the following problem:

    • Extended diagnostic time
    • Incorrect diagnosis
    • Incorrect parts replacement

Test Description

Refer to step numbers on the diagnostic table.

  1. The inflatable restraint IP module switch must be in the ON position to perform the system diagnostic check.

    2.

  2. The AIR BAG warning lamp should flash 7 times after the ignition switch is first turned to the RUN position.

    3.

  3. The AIR BAG warning lamp indicates improper operation. This test differentiates a warning lamp stays ON condition from a warning lamp does not come ON condition.

    4.

  4. The AIR BAG warning lamp should turn OFF after flashing 7 times.

    5.

  5. This test checks for the proper operation of the serial data line.

    6.

  6. This test will identify the stored diagnostic trouble codes and whether they are current or history.

    7.

  7. This test checks for the proper operation of the serial data line.

    8.

  8. This test refers to the appropriate DTC Table Diagnostic Aids for diagnosis of the history DTCs.

SIR Diagnostic System Check

Step

Action

Value(s)

Yes

No

1

Does this vehicle have a inflatable restraint IP module switch?

--

Go to Step 2

Go to Step 3

2

  1. Turn the ignition switch to the ON position.
  2. Turn the inflatable restraint IP module switch to the OFF position and then back to the ON position.

Is the inflatable restraint IP module switch in the ON position?

--

Go to Step 3

--

3

Note 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 5

Go to Step 4

4

Does the AIR BAG warning lamp come ON steady?

--

Go to AIR BAG Warning Lamp Comes On Steady

Go to AIR BAG Warning Lamp Does Not Come On

5

Note the AIR BAG warning lamp after the AIR BAG warning lamp flashed 7 times.

Does the AIR BAG warning lamp go OFF?

--

Go to Step 9

Go to Step 6

6

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

Is a current DTC displayed?

--

Go to Step 8

Go to Step 7

7

Does the Scan Tool indicate no data received?

--

Go to Scan Tool Does Not Communicate with UART Data Line in Wiring Systems

Go to Sensing and Diagnostic Module Integrity Check

8

  1. Turn the ignition switch to the OFF position.
  2. Record the displayed DTCs on the repair order, specifying as current or history.
    3. • When DTC B1051 is set, refer to DTC B1051 Deployment Commanded .
    • When DTC B1018 is set, refer to DTC B1018 Passenger Deployment Loop Short to GND .
    • When DTC B1024 is set, refer to DTC B1024 Driver Deployment Loop Short to Ground .
  3. Diagnose the remaining DTCs from lowest to highest.
  4. When only history DTCs exist, refer to Diagnostic Aids for that specific DTC. A history DTC indicates the malfunction has been repaired or is intermittent.

Has current DTC diagnosis been performed and the current DTCs cleared?

--

Go to Step 3

--

9
  1. Turn the ignition switch to the OFF position.
  2. Connect the Scan Tool to the data link connector.
  3. Turn the ignition switch to the RUN position.
  4. Request the SIR diagnostic trouble code (DTC) display.

Is a history DTC displayed?

--

Go to Step 11

Go to Step 10

10

Does the Scan Tool indicate no data received?

--

Go to Scan Tool Does Not Communicate with UART Data Line in Wiring Repairs

System OK

11

  1. Turn the ignition switch to the OFF position.
  2. Record the displayed DTCs on the repair order specifying as history.
  3. When DTC B1071 is set, refer to DTC B1071 Internal SDM Failure .
  4. For all other DTCs, refer to Diagnostic Aids for that specific DTC. A history DTC indicates the malfunction has been repaired or is intermittent.

Has the diagnosis been performed and the DTCs cleared?

--

Go to Step 3

--