GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 Restraints 🢒 SIR 🢒 DTC 026

Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests, ignition and deployment loop voltages are measured to ensure that they are within their respective normal voltage ranges. The SDM then proceeds with the resistance measurement test. Driver low terminal A7 is grounded through a current sink, and the driver current source is connected to the driver high terminal to allow a known amount of current to flow. By monitoring the voltage difference between driver high and driver low, the SDM calculates the combined resistance of the driver inflator module, the harness wiring, and the connector terminal contacts.

Conditions for Setting the DTC
    • Resistance of the driver deployment loop is higher than 4.5 ohms for 500 milliseconds.
    • Voltage at the driver high is less than 2 volts and the resistance of the driver deployment loop is higher than or equal to 4.5 ohms for 500 milliseconds.
    • Ignition voltage is within normal operation range.

Action Taken When the DTC Sets

The SDM will turn on the AIRBAG indicator and set a diagnostic trouble code DTC 26.

Conditions for Clearing the DTC
    • Resistance of the driver deployment loop is less than or equal to 4.5 ohms for 500 milliseconds.
    • Voltage at the driver high is higher than 2 volts and the resistance of the driver deployment loop is less than 4.5 ohms for 500 milliseconds.
    • Turn OFF the ignition switch.
    • The scan tool CLEAR CODES command is received.

Diagnostic Aids

An intermittent condition is likely to be caused by a poor connection, either at the driver airbag or clock spring connectors or SDM terminals A6 and A7. An open wire in the driver deployment loop will also set DTC 26. To test for a faulty clock spring, clear the DTCs, then turn the steering wheel back and forth with the ignition switch ON. If the AIRBAG indicator comes on and DTC 26 has set again, it is likely that the clock spring is faulty.

Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section.

Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section.

Step

Action

Values

Yes

No

1

Perform the Diagnostic System Check - SIR.

Is the Diagnostic System Check - SIR complete?

--

Go to Step 2

Go Diagnostic System Check - SIR

2
  1. Turn OFF the ignition and remove the key.
  2. Make sure the clock spring yellow two-way connector, located on the steering column, is seated properly.

Is the yellow clock spring connector seated properly?

--

Go to Step 4

Go to Step 3

3
  1. Seat the clock spring yellow two-way connector.
  2. Make sure all SIR components are reconnected and all components are properly mounted.
  3. Turn ON the ignition.

Is DTC 26 still current?

--

Go to Step 4

Go to Diagnostic System Check - SIR

4
  1. Turn OFF the ignition and remove the key.
  2. Disconnect the yellow clock spring connector on the steering column.
  3. Connect a jumper between the terminals on the SDM side of the clock spring connector.

    4. Refer to Diagnostic Illustration 8 in SIR Diagnostic Illustrations .

  4. Turn ON the ignition.

Is the DTC 26 still displayed?

--

Go to Step 9

Go to Step 5

5
  1. Turn OFF the ignition and remove the key.
  2. Examine the connection at the driver airbag.

Is the driver airbag connector seated properly?

--

Go to Step 7

Go to Step 6

6
  1. Properly seat the connector to the driver airbag.
  2. Connect the yellow clock spring connector on the lower steering column.
  3. Turn ON the ignition.

Is the DTC 26 still displayed?

--

Go to Step 7

Go to Diagnostic System Check - SIR

7
  1. Turn OFF the ignition and remove the key.
  2. Disconnect the yellow clock spring connector on the steering column.
  3. Temporarily remove the driver airbag.
  4. Connect a jumper between the terminals of the clock spring-to-driver airbag connector.

    5. Refer to Diagnostic Illustration 9 in SIR Diagnostic Illustrations .

  5. Use an ohmmeter to check the continuity of the clock spring.

Is the wire open?

--

Go to Step 9

Go to Step 8

8
  1. Turn OFF the ignition and remove the key.
  2. Disconnect the yellow clock spring connector on the steering column.
  3. Replace the driver airbag. Refer to Inflatable Restraint Steering Wheel Module Replacement .
  4. Connect all SIR components and the scan tool.
  5. Turn ON the ignition.

Is DTC 26 still displayed?

--

Go to Step 1

Go to Diagnostic System Check - SIR

9
  1. Turn OFF the ignition and remove the key.
  2. Turn the steering wheel to the straight-ahead position.
  3. Disconnect the yellow clock spring connector on the steering column.
  4. Replace the clock spring.
  5. Connect all SIR components and the scan tool.
  6. Turn ON the ignition.

Is DTC 26 still displayed?

--

Go to Step 1

Go to Step 10

10
  1. Turn OFF the ignition and remove the key.
  2. Disconnect the passenger airbag, the yellow clock spring connector on the steering column, and the connector C221.
  3. Disconnect the SDM connector.
  4. Examine the pins and terminals at the SDM terminals A6 and A7.

Are there any loose wires or backed-out terminals?

--

Go to Step 11

Go to Step 12

11
  1. Repair any loose wires or damaged pins or terminals.
  2. Connect all SIR components and the scan tool.
  3. Turn ON the ignition.

Did you complete the repair?

--

Go to SIR Diagnostic Illustrations

--

12

Use an ohmmeter to check both driver deployment wires for an open circuit between the SDM connector, terminals A6 and A7, and the clock spring connector.

Refer to Diagnostic Illustration 16 in SIR Diagnostic Illustrations .

Is either wire open?

∞

Go to Step 13

Go to Step 14

13
  1. Replace any open wires between the SDM and the clock spring.
  2. Connect all SIR components and the scan tool.
  3. Turn ON the ignition.

Is DTC 26 still current?

--

Go to Step 14

--

14
  1. Turn OFF the ignition and remove the key.
  2. Disconnect the passenger airbag, the yellow clock spring connector on the steering column and connector C221.
  3. Replace the SDM. The arrow must be pointing toward the front of the vehicle.
  4. Connect all SIR components, and ensure that all components are properly mounted.
  5. Command CLEAR CODES with the scan tool.

Did you complete the repair?

--

Go to Diagnostic System Check - SIR

--