GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Montana Ext. 🢒 Restraints 🢒 SIR 🢒 DTC B0077

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 inflatable restraint side impact sensor (SIS) - LF. When the input power is detected, the SIS responds by performing internal diagnostics. After that, the SIS 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 is powered up. The SIS will continually communicate a status message to the SDM. The SDM can reset the SIS 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 SIS being powered up
    • A valid ID message is not received
    • The SDM has failed twice to reset the SIS

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 SIS.

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 SIS - LF voltage circuit and the SIS - LF signal circuit
    • A short to ground, short to voltage, open, or high resistance in the SIS - LF voltage circuit or the SIS - LF signal circuit
    • The SIS connector
    • An internal SIS 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 SIS connector is damaged or corroded.

    2.

  2. Tests to see if the SIS 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 SIS - LF voltage circuit and the SIS - LF signal circuit.

    6.

  6. Tests to see if there is an open or high resistance in the SIS - LF voltage circuit or the SIS - LF signal circuit.

    7.

  7. Tests to see if there is a short to ground or a short to voltage in the SIS - LF voltage circuit or the SIS - LF signal circuit.

Step

Action

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 SIS connector. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  3. Inspect the SIS 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 SIS terminals for damage or corrosion that may cause the malfunction.

Do the SIS 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 SIS - LF voltage circuit and the SIS - LF signal circuit for a short between the 2 circuits.

Did you find and correct the condition?

Go to Step 12

Go to Step 7

7

Test the SIS - LF voltage circuit and the SIS - LF signal circuit 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 SIS - LF voltage circuit and the SIS - LF signal circuit 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 SIS. Refer to Inflatable Restraint Side Impact 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