GM Service Manual Online
For 1990-2009 cars only

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 B0685 01: Security System Indicator Circuit Short to Battery

DTC B0685 06: Security System Indicator Circuit Short to Ground or Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Security Indicator Control

B0685 06

B0685 06

B0685 01

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Circuit/System Description

The security indicator is controlled by the body control module (BCM) based on commands from the immobilizer system or the content theft deterrent (CTD) system. With the ignition OFF, the security indicator is commanded by the CTD system. With the ignition ON, the security indicator is commanded by the immobilizer system.

The security indicator is located in the instrument panel cluster (IPC) and is supplied B+ at all times. When the immobilizer or CTD system requests the indicator be commanded ON, the BCM grounds the security indicator control circuit, illuminating the indicator.

Conditions for Running the DTC

Battery voltage is 9-16 volts

Conditions for Setting the DTC

B0685 01

The BCM detects a short to ground on the security indicator control circuit.

B0685 06

The BCM detects a short to voltage or an open on the security indicator control circuit.

Action Taken When the DTC Sets

Security indicator output is disabled.

Conditions for Clearing the DTC

    • A current DTC is cleared when the conditions for setting the DTC are no longer present.
    • A history DTC will clear after 40 malfunction free ignition cycles.

Reference Information

Schematic Reference

Theft Deterrent System Schematics

Connector End View Reference

Displays and Gages Connector End Views

Description and Operation

Content Theft Deterrent (CTD) Description and Operation

Electrical Information Reference

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

Circuit/System Verification

Ignition ON, command the security indicator ON and OFF with a scan tool. The security indicator should turn ON and OFF when changing between the commanded states.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the IPC.
  2. Connect a test lamp between the control circuit terminal 10 (HHR) or 14 (Cobalt, G5) and B+.
  3. Ignition ON, command the Security LED ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  4. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM or IPC replacement, programming, and setup