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 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 illuminate solid on the IPC for approximately 3 seconds then flash 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 Passlock Theft Deterrent Systems.

An unrecognized or incorrect password is sent to the PCM from the 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 a poor connection, a rubbed through wire insulation, or by a broken wire inside the insulation.

Thoroughly inspect any suspected circuitry for the following items:

The numbers below refers to the step numbers on the diagnostic table:

2. The scan tool can display whether or not the BCM has received and learned the password from the lock cylinder. If the password is not received, the reason the PCM set this DTC may due to a password that has not yet been learned due to a component being replaced, or a problem in the BCM or a VTD component.

3. 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.

4. A BCM Passlock theft deterrent DTC being set indicates that a Passlock II component may be malfunctioning.

5. The replacement PCM must be programmed, and the Crankshaft Position System Variation Learn procedure must be performed. A programmed PCM does not require the password learn procedure to be performed. The password will be learned on the first ignition cycle.