The Vehicle Theft Deterrent (VTD) System, called a Passlock II System, is designed to prevent vehicle theft by disabling the engine unless the Passlock lock cylinder is correctly engaged by a mechanical key. The Passlock II System utilizes four components for theft detection: the lock cylinder, the ignition switch, the Body Control Module (BCM) and the Powertrain Control Module (PCM).

When starting the engine, the PCM looks for a password from the Body Control Module (BCM) through the Class 2 serial data circuit. If the password is not recognized or not present, the PCM will disable the engine. If an incorrect or no Password received, this indicates that the engine will start and stall immediately. THEFT SYSTEM telltale will flash on the IPC for approximately 4 seconds. If an incorrect or Disable Password Received , (More than three invalid passwords are received) this indicates that the engine is disabled for at least 10 minutes and that the THEFT SYSTEM telltale will flash on the IPC for approximately 4 seconds then illuminate solid on the Instrument Panel Cluster (IPC) for the 10 minutes.

After the vehicle has passed theft detection, the PCM will continue a normal engine operation. If the PCM loses the BCM communication within the same ignition cycle, the vehicle will continue to run on the following ignition cycles. This mode is called the fail enable mode. Additional information can be found in the Theft Deterrent section.

A password (other than the Fuel Disabled or Undecided password) that does not match is sent to the Powertrain Control Module (PCM) from the body control module (BCM).

Attempting to start the vehicle by bypassing the Passlock ll system or by substituting parts without performing the password learn procedure may set a DTC P1631 and a P1632.

If no password is received, a DTC U1064 and P1632 may be set.

An intermittent may be caused by the following conditions:

Thoroughly check any suspected circuitry for the following items:

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.

3. A BCM Passlock theft deterrent DTC being set indicates that a Passlock II component may be malfunctioning. Refer to the applicable BCM table for diagnosis.

4. The theft deterrent password resides in the Body Control Module (BCM). Anytime a VTD component is replaced, the Powertrain Control Module (PCM) must relearn the new BCM password. Refer to Password Learn .

6. Replacement PCMs must be reprogrammed. A reprogrammed PCM does not require the password learn procedure to be performed. The password will be learned on the first ignition cycle. Refer to the latest Techline information for programming procedures. The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM reprogramming and the Crankshaft Position System Variation Learn abortion of the service manual for the Crankshaft Position Variation Procedure.

8. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.