GM Service Manual Online
For 1990-2009 cars only

The CTD system (when armed) is designed to deter vehicle content theft by pulsing the horns and exterior lamps for approximately 2 minutes when an unauthorized vehicle entry is detected. However, the CTD system does not affect engine starting.

An unauthorized entry can be any of the following with the CTD system armed:

    • Forced entry into the passenger compartment.
    • When any door is opened without being unlocked by using the key to unlock either of the front doors or the UNLOCK command from a Keyless Entry Transmitter.
    • Forced entry into the rear compartment.

The components of the system are:

    • Keyless Entry Module (Remote Control Door Lock Receiver)
    • Door Ajar Switches
    • Body Control Module
    • Front Door Lock Cylinder Switches
    • Power Door Lock Switches

Arming the CTD System

Use the following procedure in order to arm the system:

  1. Place the shift lever in P (park).
  2. Turn OFF the ignition.
  3. Open any door.
  4. Important: The system is not armed if the doors are locked manually, the power door lock switch or remote keyless entry transmitter must be used to arm the CTD system.

  5. Lock the doors with the power door lock switch or the LOCK button on the transmitter. The system is in standby mode and will not start the arming timer until all doors are closed.
  6. The system will arm approximately 30 seconds from the time that the last door is closed. This delay is shown by the SECURITY indicator ON STEADY. When the indicator transitions to OFF, the system is armed.

Locking The Vehicle Without Arming The CTD System

Locking the vehicle may be accomplished without arming the CTD system. Use of the manual door locks or using the key to lock the doors will lock the vehicle but will not arm the CTD system.

Disarming an armed system/silencing an alarm

If system arming has been requested by the power door lock switch or the keyless entry transmitter, it must be disarmed.

Important: Using the power door unlock switch or manually unlocking the doors does not disable the CTD arm mode. Also, disconnecting the battery or pulling fuses does not disable the arm mode, since the BCM stores the CTD mode status in memory.

    • To disarm the CTD system in standby mode (SECURITY indicator flashing and door(s) open), perform one of the following:
       - Press either power door unlock switch.
       - Use a key to unlock either front door.
       - Press the UNLOCK button on the keyless entry transmitter.
       - Insert a valid key into the ignition and switch to the ON position.
    • To disarm the CTD system in the armed mode:
       - Use the key to unlock the either front door.
       - Press the UNLOCK button on the keyless entry transmitter.
       - Insert a valid key into the ignition and switch to the ON position
    • To disarm the CTD system when activated (alarming mode).
       - Use the key to unlock either front door.
       - Press the UNLOCK button on the keyless entry transmitter.
       - Insert a valid key into the ignition and switch to the ON position.

CTD Circuit Description

The following is a description of each component used in the CTD system:

Keyless Entry Module (Remote Control Door Lock Receiver)

The keyless entry system can arm and disarm the CTD system. When the keyless entry module receives a door lock or unlock signal from the transmitter, the keyless entry module sends a message to the BCM on the keyless entry serial data link to perform the appropriate arm/disarm functions.

Door Ajar Switches

The CTD system uses the door ajar switches in the door lock assemblies as one method to activate the alarm. The body control module (BCM) monitors all door ajar switches via a discrete input from each door ajar switch, including the rear compartment. If the BCM receives a ground signal from a door ajar switch when the CTD system is armed, the BCM activates the alarm.

Body Control Module (BCM)

The CTD system is an internal function of the Body Control Module (BCM) which utilizes class 2 serial data and various switch input information to perform CTD functions. When the BCM detects an unauthorized entry, it activates the horns and exterior lamps. The BCM has five basic modes (disarmed, standby, delayed, armed, and alarm) for operating the CTD system. The different modes are described below.

  1. The BCM has the CTD system in a disarmed mode until the following conditions are detected:
  2. • Ignition key turned to the OFF position.
    • Any door open.
    • Doors locked by either the power door lock switch or the LOCK button on the transmitter.
  3. The BCM enters the standby mode when the above conditions are detected. In standby mode, the BCM commands the SECURITY indicator to flash. If all the doors are closed and the LOCK button on the transmitter is used, the BCM enters the delayed mode.
  4. When the last door is closed, the BCM enters the delayed mode for 30 seconds. In delayed mode the BCM commands the SECURITY indicator to illuminate ON steady.
  5. After 30 seconds, the BCM enters the armed mode. Any forced entry activates the alarm mode.
  6. When the BCM detects a forced entry, the BCM enters the alarm mode. The BCM activates the horns and exterior lamps for 2minutes. This is followed by a three minute time-out with the horn no longer active. If no new intrusions are detected after the time-out, the horn is not active.The system must be disarmed or the intrusion condition removed after the time-out for the system to exit alarm mode.

Front Door Lock Cylinder Switches

The door lock cylinder switches located in the driver and front passenger doors are a discrete input to the BCM. The BCM utilizes each of these inputs to disarm the CTD system. Inserting a key and turning to the unlock position will disarm the CTD system.

Power Door Lock Switches

The power door lock switches are used to either arm or disarm the CTD system. Pressing the lock position will cause the CTD to arm after all doors are closed and the 30 second delay period has elapsed. Pressing the unlock position will disarm the CTD system.

Important

The CTD system can be armed with the windows or sunroof open.

Inputs

The BCM monitors the following inputs:

    • Driver and passenger door ajar switches
    • Driver and passenger power door lock/unlock switches
    • Front door lock cylinder disarm switches
    • Rear compartment ajar switch
    • Transmitter LOCK/UNLOCK buttons, class 2 message from the Remote Keyless Entry (RKE) Module

Outputs

The BCM controls the following:

    • The horn relay
    • The exterior lights