GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Envoy - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC B0024

Circuit Description

When the ignition is first turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM then performs the following continuous diagnostic tests on the deployment loops:

    • Deployment loop voltage out of range test
    • Deployment loop resistance measurement test

If the voltage out of range test detects a short to voltage condition, the resistance measurement test for that deployment loop will not be performed.

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC
    • The SDM detects the voltage at driver frontal high is greater than 6 volts for 500 milliseconds.
    • The SDM detects the voltage at driver frontal high is less than 2.4 volts and driver frontal deployment loop resistance is less than 6 ohms for 500 milliseconds.

Action Taken When the DTC Sets
    • The SDM disables the driver frontal deployment loop resistance test.
    • The SDM commands ON the AIR BAG indicator via Class 2 serial data.
    • The SDM also sets this DTC as current after an accident. The SDM will write the status of this DTC to the "crash log" area of the EEPROM for retrieval.

Conditions for Clearing the DTC
    • You issue a scan tool CLEAR DTCs command.
    • A history DTC will clear once 255 malfunctions free ignition cycles have occurred.

When the SDM detects that no DTCs are present, the SDM commands the AIR BAG indicator OFF.

Diagnostic Aids

The following can cause an intermittent condition:

    • A short between the driver frontal high and the driver frontal low circuits.
    • A malfunctioning shorting bar on the inflatable restraint steering wheel module 2-way connector.
    • A malfunctioning shorting bar on the inflatable restraint steering wheel module coil 2-way connector.

Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step inspects the in-line connector below the inflatable restraint steering wheel module coil.

    2.

  2. Tests for the proper operation of the inflatable restraint steering wheel module coil and/or inflatable restraint steering wheel module.

    3.

  3. Tests for a short to ground in the driver frontal high deployment circuit.

    4.

  4. Tests for a short to ground in the driver frontal low deployment circuit.

    5.

  5. Tests for a short to voltage in the driver frontal high deployment circuit.

  6. Tests for a short to voltage in the driver frontal low deployment circuit or if there is a malfunctioning SDM.

Step

Action

Value(s)

Yes

No

Schematic Reference: SIR Schematics

1

Did you perform the Diagnostic System Check - SIR?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Turn OFF the ignition.
  2. Disconnect the inflatable restraint steering wheel module coil in-line harness connector located at the base of the steering column.
  3. Inspect both halves of the connector for the following conditions:
    4. • Corrosion
    • Terminal damage
    • Poor connections/terminal tension

Do the connectors exhibit any signs of corrosion, terminal damage, or poor connections?

--

Go to Step 3

Go to Step 4

3
  1. Replace the wiring harness side of the in-line connector. Refer to Connector Repairs in Wiring Systems.
  2. If the steering wheel module coil connector exhibits any of the above conditions, the module must be replaced. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 18

--

4
  1. Reconnect the in-line connector.
  2. Verify that the connector position assurance (CPA) is properly installed.
  3. Turn ON the ignition, with the engine OFF.
  4. Use the scan tool to request the SIR DTC display.

Does the scan tool indicate that DTC B0024 is current?

--

Go to Step 5

Go to Diagnostic Aids

5
  1. Turn OFF the ignition.
  2. Disconnect the steering wheel module coil in-line harness connector located at the base of the steering column.
  3. Use the J 38715-100 adaptor to connect the J 38715-A SIR Load Tool to the wiring harness side of the in-line connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Use the scan tool to request the SIR DTC display.

Does the scan tool indicate that DTC B0024 is current?

--

Go to Step 9

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Remove the steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .
  3. Disconnect the J 38715-A SIR Load Tool and adaptor.
  4. Reconnect the in-line connector.
  5. Use the J 38715-30A adaptor to connect the J 38715-A SIR Load Tool to the upper steering wheel module coil connector on the steering column.
  6. Turn ON the ignition, with the engine OFF.
  7. Use the scan tool to request the SIR DTC display.

Does the scan tool indicate that DTC B0024 is current?

--

Go to Step 8

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Replace the steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

8
  1. Turn OFF the ignition.
  2. Replace the steering wheel module coil. Refer to Inflatable Restraint Steering Wheel Module Coil Replacement .

Did you complete the replacement?

--

Go to Step 18

--

9

  1. Turn OFF the ignition.
  2. Disconnect the inflatable restraint sensing and diagnostic module (SDM) harness connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  3. Disconnect the J 38715-A SIR Load Tool and adaptor.
  4. Using J 39200 DMM measure the resistance between the SDM harness connector driver frontal high circuit and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure less than the specified value?

OL

Go to Step 10

Go to Step 11

10

Locate and repair a short to ground in the driver frontal high circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

11

Using J 39200 DMM measure the resistance between the SDM harness connector driver frontal low circuit and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure less than the specified value?

OL

Go to Step 12

Go to Step 13

12

Locate and repair a short to ground in the driver frontal low circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

13

  1. Turn ON the ignition, with the engine OFF.
  2. Using J 39200 DMM measure the voltage between the SDM harness connector driver frontal high circuit and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the voltage measure less than the specified value?

1 V

Go to Step 15

Go to Step 14

14

Locate and repair a short to voltage in the driver frontal high circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

15

Using J 39200 DMM measure the voltage between the SDM harness connector driver frontal low circuit and a known good ground. Refer to Circuit Testing in Wiring Systems.

Does the voltage measure less than the specified value?

1 V

Go to Step 17

Go to Step 16

16

Locate and repair a short to voltage in the driver frontal low circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

17

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

Did you complete the replacement?

--

Go to Step 18

--

18
  1. Reconnect all SIR system components.
  2. Verify that all components, connectors and CPAs are properly mounted.
  3. Use the scan tool in order to clear the DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK