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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 Yukon - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC B0100, B0101, B0102, B0103, B0104, or B0105

Circuit Description

The inflatable restraint front end sensor utilizes a unidirectional 2-wire circuit. The front end sensor modulates current on the interface to send ID, State of Health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the front end sensor. When the ignition is turned on and input power from the SDM is first detected, the front end sensor responds by performing internal diagnostics and sending an ID to the SDM. The SDM considers the ID to be valid if the response time is less than 5 seconds. The front end sensor continually communicates status messages to the SDM, which determines if a fault is present in the front end sensor circuit. When a fault is detected, the SDM resets the front end sensor twice by removing and reapplying power. If the fault is still present, the SDM will set a diagnostic trouble code (DTC).

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC
    • DTC B0100 and B0103 will set when one of the following conditions occur:
       - A valid ID message is not received within 5 seconds of the front end sensor being powered up.
       - Status message is not received.
       - The SDM has failed twice to reset the front end sensor.
    • DTC B0102 and B0105 will set when one of the following conditions occur:
       - The SDM has received an ID message from the front end sensor which does not match the ID stored in the SDM memory.
       - When two front end sensor resets are attempted without the correct identification being detected by the SDM.
    • DTC B0101 and B0104 will set when the SDM has received 4 consecutive NOK (Not OK) messages from the front end sensor.

Action Taken When the DTC Sets
    • The SDM commands the AIR BAG indicator ON via Class 2 serial data.
    • The SDM attempts to reset the front end sensor.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • You issue a scan tool CLEAR DTCs command.
    • A history DTC will clear once 255 malfunction free ignition cycles have occurred.

Diagnostic Aids

The following can cause an intermittent condition:

    • A short between the front end sensor signal and low reference circuits
    • High or low resistance in the front end sensor signal and low reference circuits
    • Inspect the front end sensor signal and low reference circuits carefully for cutting and/or chafing
    • Verify that the correct front end sensor is installed in the vehicle

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 the communication status of the front end sensor.

    2.

  2. Tests for a short to ground, a high resistance, or an open in the front end sensor signal circuit.

    3.

  3. Tests for a short to ground, a high resistance, or an open in the front end sensor low reference circuit.

    4.

  4. Tests for a short to voltage in the front end sensor signal and low reference circuits.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform the Diagnostic System Check - SIR?

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, request the SIR DTC display.

Does the scan tool indicate that either DTC B0101, B0102, B0104, or B0105 is current?

Go to Step 12

Go to Step 3

3
  1. Turn OFF the ignition.
  2. If DTC B0100 is current, disconnect the left front end sensor connector (sensor 1). If DTC B0103 is current, disconnect the right front end sensor connector (sensor 2). Refer to Inflatable Restraint Front End Sensor Replacement.
  3. Inspect both front end sensor and harness connector terminals for damage or corrosion.

Do the front end sensor terminals or harness connector exhibit any signs of damage or corrosion?

Go to Step 4

Go to Step 5

4
  1. If the front end sensor terminals are damaged, replace the front end sensor. Refer to Inflatable Restraint Front End Sensor Replacement.
  2. If the front end sensor harness connector is damaged, replace the connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the replacement?

Go to Step 13

--

5
  1. Disconnect the SDM connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement.
  2. Inspect the SDM connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 6

6

  1. If DTC B0100 is current, test the left front end sensor (sensor 1) signal circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  2. If DTC B0103 is current, test the right front end sensor (sensor 2) signal circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 7

7

  1. If DTC B0100 is current, test the left front end sensor (sensor 1) low reference circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  2. If DTC B0103 is current, test the right front end sensor (sensor 2) low reference circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

8

  1. Turn ON the ignition, with the engine OFF.
  2. If DTC B0100 is current, test the left front end sensor (sensor 1) signal and low reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairsin Wiring Systems.
  3. If DTC B0103 is current, test the right front end sensor (sensor 2) signal and low reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairsin Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

9

For DTC B0100 replace the left front end sensor. For DTC B0103 replace the right front end sensor. Refer to Inflatable Restraint Front End Sensor Replacement.

Did you complete the replacement?

Go to Step 10

--

10
  1. Reconnect all SIR system 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 13

--

12

For DTC B0101 and B0102 replace the left front end sensor. For DTC B0104 and B0105 replace the right front end sensor. Refer to Inflatable Restraint Front End Sensor Replacement.

Did you complete the replacement?

Go to Step 13

--

13
  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