The personal automotive security system (PASS-Key®) is an internal function of the Body Control Module (BCM). The PASS-Key® system is designed to prevent vehicle theft by disabling the starting and fuel delivery systems unless an ignition key with a specific electrical resistance is used to start the vehicle.
There are 15 different ignition key resistance values. Of the 15 different resistance values, or key codes available, only one will work with each Body Control Module (BCM). Once the key code is programmed into the BCM, the code is stored in non-volatile memory.
The Powertrain Control Module (PCM) enables engine starting when the PASS-Key® system detects a valid coded key is being used to start the vehicle
If the wrong resistance value is sensed when the ignition switch is in the ON position, the PCM will disable the starting and fuel delivery systems for approximately 3 minutes. The security indicator will be illuminated until the 3 minute timer has expired.
Important: If the PASS-Key® system detects an open or short to ground when the ignition switch is in the ON position, the BCM will default to fail enable mode. The vehicle will not stall or stop running. If the BCM is in fail enable state when the ignition is turned OFF, it will remain fail enable until the next time the vehicle is started. If the BCM is fail enable the PASS-Key® system is NOT active and the vehicle will start. The PASS-Key® system includes the following components:
| • | Ignition key |
| • | Ignition cylinder |
| • | Body Control Module (BCM) |
| • | Crank relay |
| • | Powertrain Control Module (PCM) |
| • | SECURITY indicator |
Ignition Key
The ignition key is a typical ignition key blank with an imbedded resistor. The key blank and resistor are not serviceable separately. There are 15 different resistance values. The ignition key also has mechanical cuts similar to non PASS-Key® ignition keys.
Ignition Cylinder
The ignition cylinder contains a set of electrical contacts used to measure the resistor in the ignition key. When the ignition key is inserted into the lock cylinder, the resistor in the key makes contact with the electrical contacts inside the ignition cylinder.
Body Control Module
The PASS-Key® system is an internal function of the Body Control Module (BCM). The BCM reads the key code from the ignition cylinder when the ignition is turned to the ON position. If the code is correct, the BCM will send an enable message to the PCM via the class 2 serial data circuit. If the BCM receives the wrong code, the BCM will immediately go into tamper mode. The BCM will send a disable message to the PCM disabling the starting and fuel delivery systems.
Crank Relay
The crank relay is used to prevent the engine from cranking if the correct resistance is not sensed at the ignition key. It prevents the engine from cranking by opening the circuit to the starter solenoid.
Powertrain Control Module
The Powertrain Control Module (PCM) communicates with the Body Control Module (BCM) over the Class 2 serial data line. When the BCM enters tamper mode, it sends a Class 2 message to the PCM in order to disable the starting and fuel delivery systems. If the BCM receives a valid coded key, the BCM sends a class 2 message to the PCM in order to enable the starting and fuel delivery systems. The PCM then allows the vehicle to start.
SECURITY indicator
The SECURITY indicator is located on the instrument cluster. The SECURITY indicator is controlled by a class 2 serial data message from the BCM.
