GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC B0077

Circuit Description

Important: This DTC is also used for the inflatable restraint electronic frontal sensor (EFS) found on the 35/36 series trucks. The 35/36 series trucks have one EFS located at the front of the vehicle. The EFS is diagnosed the same way as the inflatable restraint side impact sensor (SIS) used on Utility models. The following diagnostics will refer to the left SIS or the EFS depending on what series truck you are diagnosing.

The SIS/EFS circuit consists of a SIS/EFS, the SIS/EFS signal circuit, and the SIS/EFS voltage circuit. When the ignition is turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM provides input power to the SIS/EFS. When input power is first detected, the SIS/EFS responds by performing internal diagnostics. The SIS/EFS then 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 SIS/EFS is powered up. The SIS/EFS will continually communicate a status message to the SDM. The SDM is capable of resetting the SIS/EFS 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
    • A valid ID message is not received within 5 seconds of the left SIS/EFS being powered up.
    • Status message is not received.
    • The SDM has failed twice to reset the left SIS/EFS.

Action Taken When the DTC Sets
    • The SDM commands ON the AIR BAG indicator via Class 2 serial data.
    • The SDM attempts to reset the left SIS/EFS.

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 left SIS/EFS signal and voltage circuits
    • High or low resistance in the left SIS/EFS signal and voltage circuits
    • Inspect the left SIS/EFS signal and voltage circuits carefully for cutting and/or chafing

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 for a short to ground, a high resistance, or an open in the left SIS/EFS signal circuit.

    2.

  2. Tests for a short to ground, a high resistance, or an open in the left SIS/EFS voltage circuit.

    3.

  3. Tests for a short to voltage in the left SIS/EFS signal circuit.

    4.

  4. Tests for a short to voltage in the left SIS/EFS voltage circuit.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

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 left SIS/EFS connector. Refer to Inflatable Restraint Side Impact Sensor Replacement or Inflatable Restraint Front End Discriminating Sensor Replacement .
  3. Inspect the left SIS/EFS 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 11

Go to Step 3

3
  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 11

Go to Step 4

4

Test the left SIS/EFS 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 11

Go to Step 5

5

Test the left SIS/EFS voltage 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 11

Go to Step 6

6

  1. Turn ON the ignition, with the engine OFF.
  2. Test the left SIS/EFS signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

Test the left SIS/EFS voltage circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 8

8

Replace the left SIS/EFS. Refer to Inflatable Restraint Side Impact Sensor Replacement or Inflatable Restraint Front End Discriminating Sensor Replacement .

Did you complete the replacement?

Go to Step 9

--

9
  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 10

System OK

10

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

Did you complete the replacement?

Go to Step 11

--

11
  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