GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B0077, B0079, or B0080

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 B0077: Left Side Impact Sensor (SIS) Malfunction

DTC B0079: Incorrect Left Side Impact Sensor (SIS) Installed

DTC B0080: Discard Left Side Impact Sensor (SIS)

Circuit/System 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 DTC.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC
    • DTC B0077 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 B0079 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 2 front end sensor resets are attempted without the correct identification being detected by the SDM.
    • DTC B0080 will set when the SDM has received a NOK (Not OK) message from the front end sensor.

Action Taken When the DTC Sets
    • The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator.
    • The SDM attempts to reset the front end sensor.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • 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.

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the inflatable restraint front end discriminating sensor.
  2. Ignition OFF, disconnect the harness connector at the SDM.
  3. Ignition OFF, test for less than 1.0 ohm between the low reference circuit terminal A and ground.
    4. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance.
  4. Ignition OFF, test for infinite resistance between the front end sensor signal circuit terminal B and ground.
    5. ⇒If less than the specified value, test the signal circuit for a short to ground.
  5. Ignition ON, test for less than 1.0 volt between the low reference circuit terminal A and ground.
    6. ⇒If greater than the specified range, test the low reference circuit for a short to voltage.
  6. Ignition ON, test for less than 1.0 volt between the front end sensor circuit terminal B and ground.
    7. ⇒If greater than the specified range, test the front end sensor circuit for a short to voltage.
  7. Test for less than 1.0 ohm along the front end sensor circuit terminal B and SDM terminal B5.
    8. ⇒If not within the specified range, test the signal circuit for an open/high resistance.
  8. If all circuits test normal, replace the inflatable restrain front end discriminating sensor. If the DTC resets, replace the SDM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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