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

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B1620: Right Front/Passenger Side Impact Sensor (SIS) Performance

Circuit/System Description

The inflatable restraint front end sensor utilizes a bidirectional 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 may reset the front end sensor up to 2 times by removing and reapplying power to it. If the fault is still present, the SDM will set a DTC.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

Any of the following conditions exist for 2 seconds:

    • The side impact sensor circuit is shorted.
    • The side impact sensor circuit is open.
    • Right front side impact sensor malfunction.
    • Right rear side impact sensor malfunction.
    • SDM malfunction.

Action Taken When the DTC Sets
    • The SDM commands the AIR BAG indicator ON.
    • The SIR System is disabled and no deployments are allowed.

Conditions for Clearing the DTC
    • The condition for setting the DTC no longer exists.
    • A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Testing for Intermittent Conditions and Poor Connections
    •  Connector Repairs
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Testing

Important: Refer to SIR Service Precautions .

When removing connectors, inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector:

   • The front end sensor
   • The SDM module
   • The front end sensor wiring harness connector
   • The SDM wiring harness connector

  1. Ignition OFF, disconnect the harness connector at the SDM and the right front side impact sensor.
  2. Ignition ON, test for less than 1 volt between the signal circuit terminal 8 and ground.
    3. ⇒If greater than the specified range, repair the circuit for a short to voltage.
  3. Ignition ON, test for less than 1 volt between the low reference circuit terminal 11 and ground.
    4. ⇒If greater than the specified range, repair the circuit for a short to voltage.
  4. Test for infinite resistance between the signal circuit terminal 8 and ground.
    5. ⇒If less than infinite resistance, repair the circuit for a short to ground.
  5. Test for less than 1 ohm between right front side impact sensor terminal 4 and SDM harness connector terminal 8.
    6. ⇒If greater than the specified range, repair the circuit for an open/high resistance.
  6. Test for less then 1 ohm between right side impact sensor terminal 3 and SDM harness connector terminal 11.
    7. ⇒If greater than the specified range, repair the circuit for an open/high resistance.
  7. Ignition OFF, disconnect the harness connector at the right rear side impact sensor and the right front side impact sensor.
  8. Ignition ON, test for less than 1 volt between the signal circuit terminal 1 and ground.
    9. ⇒If greater than the specified range, repair the circuit for a short to voltage.
  9. Ignition ON, test for less than 1 volt between the low reference circuit terminal 2 and ground.
    10. ⇒If greater than the specified range, repair the circuit for a short to voltage.
  10. Test for infinite resistance between the signal circuit terminal 1 and ground.
    11. ⇒If less than infinite resistance, repair the circuit for a short to ground.
  11. Test for less than 1 ohm between right front side impact sensor terminal 1 and right rear side impact sensor terminal 2.
    12. ⇒If greater than the specified range, repair the circuit for an open/high resistance.
  12. Test for less then 1 ohm between right front side impact sensor terminal 2 and right rear side impact sensor terminal 1.
    13. ⇒If greater than the specified range, repair the circuit for an open/high resistance.
  13. If all circuits test normal, reconnect all SIR components.
  14. Disconnect the harness connector at the rear side impact sensor.
  15. Ignition ON, with a scan tool clear and check for DTC B1620.
    16. ⇒If the DTC does not return, replace the rear side impact sensor.
    ⇒If the DTC returns and is current, replace the front side impact sensor.
  16. Reconnect all SIR components. Ignition ON, with a scan tool clear and check for DTC B1620.
    17. ⇒If the DTC does not return, replace the rear side impact sensor.
    ⇒If the DTC returns and is current, replace the front side impact sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Inflatable Restraint Front End Sensor Replacement
    •  Inflatable Restraint Side Impact Sensor Replacement
    •  SIR/SRS Wiring Repairs
    •  Control Module References for SDM replacement, setup, and programming