GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Envoy - 4WD 🢒 DTC 🢒 DTC B1026 Driver Deployment Loop Open

Object Number: 398747 Size: SF
Cell 47: Power, Ground, DLC and Sensors
SIR Schematic Icons
Handling ESD Sensitive Parts Notice
SIR Components
Cell 47: Seat Belt Switch, Steering Wheel and IP Module
SIR Handling Caution

Circuit Description

When you first turn the ignition switch to the RUN position, the inflatable restraint sensing and diagnostic module (SDM) performs tests in order to diagnose critical malfunctions within the SDM. Next, the SDM measures IGNITION 1 voltage in order to ensure that the voltage is within the 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 SIDE HIGH and DRIVER SIDE LOW.

Conditions for Setting the DTC
    • The voltage difference between DRIVER SIDE HIGH terminal 2 and DRIVER SIDE LOW terminal 3 is more than or equal to 400 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.
    • The SDM turns the AIR BAG warning lamp to the ON position.

Conditions for Clearing the DTC
    • Current DTC
        The voltage difference between DRIVER SIDE HIGH terminal 2 and DRIVER SIDE LOW terminal 3 is less than 400 millivolts for 500 milliseconds.
    • History DTC
       - You issue a scan tool CLEAR CODES command.
       - After 250 malfunction free ignition cycles have occurred.

Diagnostic Aids

The following items 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 terminals A and B
    • A poor connection at the SDM terminals 2 and 3
    • 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 RUN position. The inflatable restraint steering wheel module coil is unlikely to malfunction if the AIR BAG warning lamp comes ON and DTC B1026 has set again.

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 determines the deployment loop voltage difference measured by the inflatable restraint sensing and diagnostic module.

    2.

  2. This test inspects 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 inspects for proper contact or corrosion of the inflatable restraint sensing and diagnostic module 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.

DTC B1026 -- Driver Deployment Loop Open

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 DLC.
  3. Turn the ignition switch to the RUN position.
  4. Request the SIR data list display.
  5. Read and record on the repair order the driver deployment loop voltage difference DRIVER VDIF.

Has the DRIVER VDIF been read and recorded on the repair order?

--

Go to Step 3

--

3
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the inflatable restraint steering wheel yellow 2-way connector at the base of the steering column and the IP module yellow 2-way connector located behind the glove box.
  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 .

Is the repair complete?

--

Go to Step 5

--

5

Inspect 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

Inspect 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 .

Is the repair complete?

--

Go to Step 23

--

8
  1. Connect the 2-way harness connectors.
  2. Turn the ignition switch to the RUN position.
  3. Use the Scan Tool in order to request the SIR data list display.
  4. Read the driver deployment loop voltage difference DRIVER VDIF.

Is the DRIVER VDIF less than the specified value?

400 mV

Go to Step 9

Go to Step 10

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

Is the repair complete?

--

Go to Step 23

--

10
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the inflatable restraint steering wheel yellow 2-way connector at the base of the steering column and IP module yellow 2-way connector located behind the glove box.
  3. Connect the J 38715-A SIR Driver/Passenger Load Tool to the harness connectors.
  4. Turn the ignition switch to the RUN position.
  5. Use the Scan Tool in order to request the SIR data list display.
  6. Read the driver deployment loop voltage difference DRIVER VDIF.

Is the DRIVER VDIF less than the specified value?

400 mV

Go to Step 11

Go to Step 14

11
  1. Turn the ignition switch to the OFF position.
  2. Remove the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
  3. Disconnect the J 38715-A SIR Driver/Passenger Load Tool from the driver yellow 2-way harness connector.
  4. Reconnect the driver yellow 2-way connector.
  5. Connect the J 38715-A SIR Driver/Passenger Load Tool to the upper inflatable restraint steering wheel module coil.
  6. Turn the ignition switch to the RUN position.
  7. Use the Scan Tool in order to request the SIR data list display.
  8. Read the driver deployment loop voltage difference VDIF.

Is the DRIVER VDIF less than the specified value?

400 mV

Go to Step 12

Go to Step 13

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

Is the repair complete?

--

Go to Step 23

--

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

Is the repair complete?

--

Go to Step 23

--

14
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Disconnect the J 38715-A SIR Driver/Passenger Load Tool.
  4. Inspect for proper connection at terminals 2 and 3 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 Wiring Repair .

Is the repair complete?

--

Go to Step 16

--

16

Inspect for proper connection at terminals 2 and 3 of the SDM.

Are the terminals damaged or corroded?

--

Go to Step 18

Go to Step 23

17

Inspect for proper connection at terminals 2 and 3 of the SDM.

Are the terminals damaged or corroded?

--

Go to Step 18

Go to Step 19

18

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

Is the repair complete?

--

Go to Step 23

--

19
  1. Zero the J 39200 Digital Multimeter.
  2. Measure the resistance from the SDM harness connector terminal 2 to the inflatable restraint steering wheel module yellow 2-way harness connector terminal A.

Is the resistance reading within the specified values?

0-0.5 ohms

Go to Step 21

Go to Step 20

20

Repair the high resistance condition in CKT 347.

Is the repair complete?

--

Go to Step 23

--

21

Measure the resistance from the SDM harness connector terminal 3 to the inflatable restraint steering wheel module yellow 2-way harness connector terminal B.

Is the resistance reading within the specified values?

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.

Is the repair complete?

--

Go to Step 23

--

23
  1. Reconnect all of the SIR system components.
  2. Ensure that all of the components are properly mounted.

Have all of 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

--