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.

Circuit/System Description

The content theft deterrent (CTD) system is a software based system in which the body control module (BCM) actively monitors certain inputs to determine if unauthorized vehicle access is being attempted. Based on inputs such as the door ajar switches, the liftgate ajar switch, and the hood ajar switch, the BCM determines whether a CTD alarm is warranted. If unauthorized access is being detected, the BCM will pulse the vehicle horn and flash the turn signals as a means of theft deterrent.

Reference Information

Schematic Reference

Theft Deterrent System Schematics

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

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

  1. Ignition ON, while opening and closing each vehicle door, verify that the applicable scan tool door ajar switch parameter cycles between Inactive/Door Closed and Active/Door Ajar.
  2. If the scan tool parameter does not cycle between the specified values, refer to Door Ajar Indicator Malfunction .
  3. Insert the vehicle key into the driver door key cylinder and rotate the cylinder between the lock and unlock positions. Verify the scan tool Door Key Cyl. Unlock Switch parameter cycles between Idle and Unlock.
  4. If the scan too parameter does not cycle between the specified parameters, refer to Content Theft Deterrent (CTD) Does Not Disarm with Key Lock .
  5. Completely lower the driver door window and close all vehicle doors.
  6. Ignition OFF, arm the CTD system using the keyless entry system by pressing the transmitter LOCK button twice. Verify the scan tool CTD Status parameter displays Armed.
  7. If the parameter does not equal the specified value, refer to Keyless Entry System Inoperative .
  8. Without disarming the system, reach in through the open driver window, unlock and open the driver door. Verify the scan tool CTD Status parameter displays Alarm Active.
  9. If the parameter does not equal the specified value, replace the BCM.
  10. With the door open, verify the vehicle horn is pulsing and the exterior lamps are flashing.
  11. If the horn is not pulsing, refer to Horns Malfunction .
    If the exterior lights are not flashing, refer to Headlamps Malfunction .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup and programming