GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 2WD 🢒 Restraints 🢒 SIR 🢒 DTC B0100

Circuit Description

When the ignition is turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Then, the SDM provides input power to the electronic frontal sensor(EFS Left), also known ai front end discriminating sensor.. When the input power is detected, the EFS Left responds by performing internal diagnostics. After that, the EFS Left sends an ID message to the SDM. The SDM will consider this to be a valid ID if the response time is less than 5 seconds after the EFS Left is powered up. The EFS Left will continually communicate a status message to the SDM. The SDM can reset the EFS Left by removing and applying power to it.

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The DTC will set if one of the following conditions occur:

    • A valid ID message is not received by the SDM within 5 seconds of the EFS Left being powered up
    • A status message is not received
    • The SDM has failed twice to reset the EFS Left

Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON via Class 2 serial data.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.
    • A history DTC will clear once 255 malfunction free ignition cycles have occurred.

Diagnostic Aids

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and the connectors may result in misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • A short between the EFS Left circuits
    • A short to ground, short to voltage, open, or high resistance in the EFS Left circuits.
    • The EFS Left connector
    • An internal EFS Left malfunction
    • The SDM connector
    • An internal SDM malfunction

If an intermittent condition exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. Tests to see if the EFS Left connector is damaged or corroded.

    2.

  2. Tests to see if the EFS Left terminals are damaged or corroded.

    3.

  3. Tests to see if the SDM connector is damaged or corroded.

    4.

  4. Tests to see if the SDM terminals are damaged or corroded.

    5.

  5. Tests to see if there is a short between the two EFS Left circuits.

    6.

  6. Tests to see if there is an open or a high resistance in the two EFS Left circuits.

    7.

  7. Tests to see if there is a short to ground or a short to voltage in the two EFS Left circuits.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform A Diagnostic System Check - SIR?

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Turn OFF the ignition.
  2. Disconnect the EFS Left connector. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .
  3. Inspect the EFS Left connector for damage or corrosion that may cause the malfunction.

Did you find and correct the condition?

Go to Step 12

Go to Step 3

3

Inspect the EFS Left terminals for damage or corrosion that may cause the malfunction.

Do the EFS Left terminals exhibit signs of damage or corrosion?

Go to Step 9

Go to Step 4

4

  1. Disconnect the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  2. Inspect the SDM connector for damage or corrosion that may cause the malfunction.

Did you find and correct the condition?

Go to Step 12

Go to Step 5

5

Inspect the SDM terminals for damage or corrosion that may cause the malfunction.

Do the SDM terminals exhibit any signs damage or corrosion?

Go to Step 11

Go to Step 6

6

Test the EFS Left circuits for a short between the two circuits.

Did you find and correct the condition?

Go to Step 12

Go to Step 7

7

Test the EFS Left circuits for an open or a high resistance.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

8

Test the EFS Left circuits for a short to ground or a short to voltage.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

9

Replace the EFS Left. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .

Did you complete the replacement?

Go to Step 10

--

10
  1. Reconnect all SIR components.
  2. Use the scan tool in order to clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 11

System OK

11

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

Did you complete the replacement?

Go to Step 12

--

12
  1. Reconnect all SIR components.
  2. Use the scan tool in order to clear the DTCs.
  3. 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