GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 XLR 🢒 Safety and Security 🢒 Seat Belts 🢒 Seat Belt 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

The inflatable restraint sensing and diagnostic module (SDM) sends the status of the seat belt switch to the instrument panel cluster (IPC) via a class 2 serial data message. If the driver seat belt is unfastened, the SDM will send a message to the IPC to illuminate the fasten safety belt indicator for 72 seconds or until the seat belt is fastened.

Reference Information

Schematic Reference

Seat Belt Schematics

Connector End View Reference

Seat Belt Connector End Views

Description and Operation

Seat Belt System Description and Operation

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Ignition ON, perform the IPC Display Test using the scan tool and verify the driver seat belt indicator is illuminated.

⇒If the indicator does not illuminate, replace the IPC.

Circuit/System Testing

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

   • IPC
   • Seat belt switch
   • Seat belt switch harness connector
   • SDM
   • SDM harness connector

  1. Ignition OFF, disconnect the harness connector at the applicable seat belt switch.
  2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the low reference circuit terminal B for an open/high resistance. If the circuit tests normal, replace the SDM.
  3. Ignition ON, verify the scan tool seat belt switch parameter is Unbuckled.
    4. ⇒If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal replace the SDM.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool seat belt switch parameter is Buckled.
    5. ⇒If not the specified value, test the signal circuit terminal A for a short to voltage or open/high resistance. If the circuit tests normal, replace the SDM.
  5. If all circuits test normal, test or replace the applicable seat belt switch.

Component Testing
  1. Ignition OFF, disconnect the harness connector at the left seat belt switch.
  2. Test for infinite resistance between the signal circuit terminal A and the low reference terminal B.
    3. ⇒If not the specified value, replace the left seat belt switch.
  3. With the seat belt buckled, test for less than 2 ohms of resistance between the signal circuit terminal A and the low reference terminal B.
    4. ⇒If greater than the specified range, replace the left seat belt switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Seat Belt Buckle Pretensioner Replacement
    •  Control Module References for SDM or IPC replacement, setup, and programming