The powertrain control module (PCM) controls the fuel injector operation based on a vehicle theft deterrent (VTD) password from the vehicle body control module (BCM). When the ignition is first turned ON, the BCM sends a programmed theft deterrent password to the PCM. The PCM acknowledges the password and responds to the BCM that normal fuel injector operation will continue. 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 is received, this indicates that the engine will start and stall immediately. The Security indicator will flash on the instrument panel cluster (IPC) for approximately 4 seconds. If an incorrect or disable password is received more than three times, this indicates that the engine is disabled for at least 10 minutes and that the Security indicator will illuminate solid on the IPC for approximately 3 seconds then flash on the IPC for 10 minutes. If the PCM loses communication with the BCM within the same ignition cycle, the vehicle will be enter fail-enable mode and continue to run on the following ignition cycles.

The ignition is cycled to ON.

The PCM receives a fuel disabled password from the BCM.

An undecided password was sent from the BCM.

Attempting to start the vehicle by bypassing the Passlock system or by substituting parts without performing the Programming Theft Deterrent System Components procedure may set a DTC P1631 and a P1632.

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

The number below refers to the step number on the diagnostic table.

4. The scan tool displays the actual voltage code sent from the Passlock cylinder. This voltage should be within 0-5 volts. If it is not, a theft deterrent B code will be set and should be diagnosed first.