GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Seville 🢒 DTC 🢒 DTC B1126 Driver Deployment Loop Open

Object Number: 142283 Size: MF
SIR Components
SIR Schematics
SIR Handling Caution
Handling ESD Sensitive Parts Notice

Circuit Description

When you first turn the ignition switch to the ON position, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Next the SDM measures Ignition 1 voltage to make sure it is within its respective normal voltage range. Then the SDM proceeds with the Deployment Loop Continuity test. During the Deployment Loop Continuity test, the SDM measures the voltage difference between Driver Frontal High and Driver Frontal Low.

Conditions for Setting the DTC
    • The voltage difference between Driver Frontal High terminal 10 and Driver Frontal Low terminal 9 is more than or equal to 426 millivolts.
    • The malfunction must be present for at least 500 milliseconds during one of the following tests:
       - Deployment Loop Continuity
       - If the malfunction is detected in this test, the Resistance Measurement test will not be performed.
       - Continuous Monitoring

Action Taken When the DTC Sets
    • The SDM sets a Diagnostic Trouble Code (DTC).
    • The SDM command the instrument cluster (IPC) to turn ON the AIR BAG warning lamp.

Conditions for Clearing the MIL/DTC
    • Current DTC
        The voltage difference between Driver Frontal High terminal 10 and Driver Frontal Low terminal 9 is less than 426 millivolts for 500 milliseconds.
    • History DTC
       - You issue a scan tool Clear DTCs command.
       - Once 250 malfunction free ignition cycles have occurred.

Diagnostic Aids

The following can cause an intermittent condition:

    • A poor connection at the inflatable restraint steering wheel module column connector terminals A and B.
    • A poor connection at the upper inflatable restraint steering wheel coil connector terminal A and B.
    • A poor connection at the SDM terminals 10 and 9.
    • An open in CKT 347.
    • An open in CKT 348.

An intermittent open in the inflatable restraint steering wheel module coil could also set this DTC. In order to test for a bad inflatable restraint steering wheel module coil, clear the DTCs, then turn the steering wheel back and forth with the ignition switch in the ON position. If the AIR BAG warning lamp comes ON and DTC B1126 has set again, it is likely the inflatable restraint steering wheel module coil is malfunctioning.

The diagnostic table directs the technician to note the scan tool value of Driver Frontal VDIF. Comparing the value of Driver Frontal VDIF can be helpful in determining if an intermittent condition exists.

When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to General Electrical Diagnosis in Wiring Systems. When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .

Test Description

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

  1. This test determines the deployment loop voltage difference measured by the inflatable restraint sensing and diagnostic module (SDM).

    2.

  2. This test checks for proper contact or corrosion of the yellow 2-way connector.

    3.

  3. This test isolates the malfunction to one side of the inflatable restraint steering wheel module coil yellow 2-way connector.

    4.

  4. This test determines whether the malfunction is due to the inflatable restraint steering wheel module or the module coil.

    5.

  5. This test checks for proper contact or corrosion of the SDM connector.

    6.

  6. This test determines whether the malfunction is in CKT 347.

    7.

  7. This test determines whether the malfunction is in CKT 348.

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 OFF.
  2. Connect a scan tool to the DLC.
  3. Turn the ignition switch to ON.
  4. Request the SIR data list display. Refer to Scan Tool Data List .
  5. Read and record on the repair order the Driver Frontal VDIF.

Has the Driver Frontal VDIF been read and recorded on the repair order?

--

Go to Step 3

--

3

  1. Turn the ignition switch OFF.
  2. Disconnect the inflatable restraint steering wheel and IP module yellow 2-way connectors at the base of the steering column and above the passenger side sound insulator.
  3. Inspect for proper connection at terminals A and B on the harness side of the inflatable restraint steering wheel module yellow 2-way connector.

Are the terminals damaged or corroded?

--

Go to Step 4

Go to Step 6

4

Replace the inflatable restraint steering wheel module yellow 2-way harness connector. Refer to Wiring Repair .

Did you complete the repair?

--

Go to Step 5

--

5

Check for proper connection at terminals A and B on the coil side of the connector.

Are the terminals damaged or corroded?

--

Go to Step 7

Go to Step 23

6

Check for proper connection at terminals A and B on the coil side of the connector.

Are the terminals damaged or corroded?

--

Go to Step 7

Go to Step 8

7

Replace the inflatable restraint steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 23

--

8
  1. Connect the 2-way harness connectors.
  2. Turn the ignition switch to ON.
  3. Using the scan tool, request the SIR data list display. Refer to Scan Tool Data List .
  4. Read the Driver Frontal VDIF.

Is the Driver Frontal VDIF greater than the specified value?

426 mV

Go to Step 10

Go to Step 9

9
  1. Turn the ignition switch OFF.
  2. Replace the inflatable restraint steering wheel module yellow 2-way harness connector. Refer to Wiring Repair .

Did you complete the repair?

--

Go to Step 23

--

10

  1. Turn the ignition switch OFF.
  2. Disconnect the inflatable restraint steering wheel and I/P module yellow 2-way connectors at the base of the steering column and above the passenger side sound insulator.
  3. Connect the J 38715-A SIR Driver/Passenger Load Tool at the harness connectors.
  4. Turn the ignition switch to ON.
  5. Using the scan tool, request the SIR data list display. Refer to Scan Tool Data List .
  6. Read the Driver Frontal VDIF.

Is the Driver Frontal VDIF greater than the specified value?

426 mV

Go to Step 14

Go to Step 11

11

  1. Turn the ignition switch OFF.
  2. Remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement for removal.
  3. Disconnect the J 38715-A Load Tool from the driver yellow 2-way harness connector.
  4. Reconnect the driver yellow 2-way connector.
  5. Connect the J 38715-A Load Tool to the upper inflatable restraint steering wheel module connector.
  6. Turn the ignition switch to ON.
  7. Using the scan tool, request the SIR data list display. Refer to Scan Tool Data List .
  8. Read the Driver Frontal VDIF.

Is the Driver Frontal VDIF greater than the specified value?

426 mV

Go to Step 13

Go to Step 12

12
  1. Turn the ignition switch OFF.
  2. Replace the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Did you complete the replacement?

--

Go to Step 23

--

13
  1. Turn the ignition switch OFF.
  2. Replace the inflatable restraint steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 23

--

14

  1. Turn the ignition switch OFF.
  2. Disconnect the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement for removal.
  3. Disconnect the J 38715-A Load Tool.
  4. Check for proper connection at terminals 10 and 9 on the harness side of the SDM connector.

Is the connector damaged or corroded?

--

Go to Step 15

Go to Step 17

15

Replace the SDM harness connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 16

--

16

Check for proper connection at terminals 10 and 9 of the SDM.

Are the terminals damaged or corroded?

--

Go to Step 18

Go to Step 23

17

Check for proper connection at terminals 10 and 9 of the SDM.

Are the terminals damaged or corroded?

--

Go to Step 18

Go to Step 19

18

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 23

--

19

Using J 39200 DMM, measure the resistance from the SDM harness connector terminal 10 to the inflatable restraint steering wheel module yellow 2-way harness connector terminal A.

Is the resistance reading within the specified values?

0.0-0.5 ohms

Go to Step 21

Go to Step 20

20

Repair the high resistance condition in CKT 347. Refer to Wiring Repair .

Did you complete the repair?

--

Go to Step 23

--

21

Using J 39200 DMM, measure the resistance from the SDM harness connector terminal 9 to the inflatable restraint steering wheel module yellow 2-way harness connector terminal B.

Is the resistance reading within the specified values?

0.0-0.5 ohms

Go to Sensing and Diagnostic Module Integrity Check

Go to Step 22

22

Repair the high resistance condition in CKT 348. Refer to Wiring Repair .

Did you complete the repair?

--

Go to Step 23

--

23

Reconnect all the SIR system components, make sure all the components are properly mounted.

Have all the SIR components been reconnected and properly mounted?

--

Go to Step 24

--

24

Clear all the SIR DTCs.

Have all the SIR DTCs been cleared?

--

Go to SIR Diagnostic System Check

--