The Passlock system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. The passlock module provides security system sensor power and low reference for the passlock sensor. the passlock module also measures the security system sensor voltage. When the correct key is used to start the vehicle, a magnet on the lock cylinder passes close to the passlock sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the passlock sensor which completes a circuit from the security sensor signal circuit through a resistor to the security sensor low reference circuit. The resistance value will vary from vehicle to vehicle. The passlock module will measure the voltage on the security sensor signal circuit and compare this voltage to a previously learned voltage. If the voltage measured is within the valid range, the passlock module will send a class 2 message to the powertrain control module (PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a class 2 message will be sent to the PCM to disable starting of the vehicle.

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.

An intermittent may be caused by a poor connection, a rubbed through wire insulation, or by a wire broken inside the insulation.

Thoroughly check any suspected circuitry for the following items:

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the fault occurred. The scan tool stores this data for later reference.

2. The PCM may not have learned the new password. Refer to Password Learn Procedure portion of the service manual.

4. 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 be 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.

5. Replacement VCMs/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.

6. A Passlock™ theft deterrent, or BCM DTC being set indicates that a Passlock™ component may be malfunctioning.

7. If no DTCs were set and the BCM has not learned (received) a password from the ignition lock cylinder, the BCM may need to learn the password, or may be malfunctioning.

9. If no malfunctions are present at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.