GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B1620

Circuit Description

The inflatable restraint side impact sensor (SIS) is a crash sensing device used in the detection of a side impact collision. The SIS is used to monitor vehicle velocity changes to detect side impact crashes that are severe enough to warrant deployment of the inflatable restraint side impact module. The SIS receives power and ground from the inflatable restraint sensing and diagnostic module (SDM). The SIS communicates the status of the side impact air bag system to the SDM via a diagnostic line. If the SDM detects a malfunction within the SIS circuit, a DTC will be set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1620 Left Front/Driver Side Impact Sensor (SIS) Performance

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The SDM detects a malfunction in the SIS - left circuits.

Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator to flash.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids

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

The following are possible causes of the malfunction:

    • An open or high resistance in the SIS - left front circuits
    • A short to ground or voltage in the SIS - left front circuits
    • A short to ground or voltage in the SIS - left rear circuits
    • A short between the SIS - left front circuits
    • A short between the SIS - left rear circuits
    • An internal SIS - left malfunction
    • An internal SDM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step tests for an open, short to ground, short to voltage or short between the SIS - left front circuits.

    2.

  2. This step tests for a short to ground, short to voltage or short between the SIS - left rear 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 - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Is DTC B1620 set as a current DTC?

Go to Step 3

Go to Diagnostic Aids

3
  1. Turn OFF the ignition.
  2. Disconnect the side impact sensor (SIS) - left front connector.
  3. Inspect both the component and harness sides of the connector for the following conditions:
    4. • Corrosion
    • Damaged terminals
    • Poor contact/terminal tension

Did you find and correct the condition?

Go to Step 12

Go to Step 4

4
  1. Disconnect the sensing and diagnostic module (SDM) connector.
  2. Inspect the SDM connector for the following conditions:
    3. • Corrosion
    • Damaged terminals
    • Poor contact/terminal tension

Did you find and correct the condition?

Go to Step 12

Go to Step 5

5

Test the SIS - left front circuits for the following conditions:

    • An open or high resistance
    • A short to ground
    • A short to voltage
    • A short between circuits
        Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 6

6

Replace the inflatable restraint SIS - left front. Refer to Inflatable Restraint Side Impact Sensor Replacement .

Did you complete the replacement?

Go to Step 7

--

7
  1. Reconnect all SIR components.
  2. Verify that all components, connectors, and connector position assurances (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 8

System OK

8

Test the SIS - left rear circuits for the following conditions:

    • A short to ground
    • A short to voltage
    • A short between circuits
        Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 9

9

Replace the inflatable restraint SIS - left rear. Refer to Inflatable Restraint Side Impact Sensor Replacement

Did you complete the replacement?

Go to Step 10

--

10
  1. Reconnect all SIR 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 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. 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