GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 Air Bag Indicator Circuit Malfunction

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.

Circuit/System Description

When the ignition is turned ON, the instrument panel cluster (IPC) flashes the air bag indicator 7 times for a bulb check. The inflatable restraint sensing and diagnostic module (SDM) performs diagnostic tests on the SIR system during the bulb check. If any malfunction exists the SDM will request the IPC to illuminate the air bag indicator steady, via serial data. If a preexisting malfunction exists, the air bag indicator will illuminate steady immediately after the ignition is turned ON. If the ignition 1 voltage is outside of the normal operating voltage range 9-16 volts, the SDM will command the IPC to illuminate the air bag indicator with no DTCs present, then disables all deployment loops.

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

Diagnostic Aids
    • If ignition 1 voltage is outside of the normal operating voltage range, 9-16 volts, the AIR BAG indicator will come ON solid with no DTCs set.
    • The loss of serial data communication between the SDM and the IPC will cause the AIR BAG indicator to come ON solid. Refer to DTC U1001-U1254 .

Circuit/System Testing
  1. Ignition ON, with a scan tool, verify the Battery Voltage Parameter is 9-16 volts.
    2. ⇒ If not the specified range, refer to Diagnostic System Check - Vehicle .
  2. Ignition OFF, monitor the IPC. With the ignition ON, the SIR warning indicator should flash then turn OFF.
    3. ⇒If the SIR warning indicator continually flashes, program the SDM.
    ⇒If the SIR warning indicator remains on steady, test for DTCs and refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  3. With a scan tool, perform the Display Test in Instrument Panel Cluster/Special Functions. The Air Bag indicator should turn ON and OFF as commanded.
    4. ⇒If the air bag indicator does not illuminate as expected, replace the IPC.
  4. Ignition OFF, disconnect the harness connector at the SDM.
  5. Ignition OFF, test for less than 1 ohm between the ground circuit terminal A18 and ground.
    6. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal A1 and ground.
    7. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  7. If all circuits test normal, test or replace the SDM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  SIR/SRS Wiring Repairs
    •  Control Module References for IPC and SDM replacement, setup, and programming