Anti-Theft - Passive
Anti-Theft - Passive
COMPONENT LOCATION
OVERVIEW
Passive Start
The passive start system relies on the detection of a uniquely coded Smart Key and low frequency antennas strategically situated within the vehicle. The antennas ensure the Smart Key is always within the active transmission zone of the antennas wherever the Smart Key is placed inside the vehicle. For this reason the orientation and positioning of the antennas is critical to the correct functioning of the system. The Smart Key also operates the passive entry system. For additional information, refer to Handles, Locks, Latches and Entry Systems
The system provides a secure interface between the CJB (central junction box) and the ECM (engine control module) to prevent unauthorized starting of the engine. This is achieved by immobilization of the engine crank system and the fuel system, using encoded data exchange between the Smart Key and multiple control modules.
Engine starting is initiated when the encoded data exchange between the Smart Key and the control modules is verified. The engine management system will then allow engine crank and fueling when an authorization data message is received from the CJB (central junction box).
The engine can be started by pressing the start/stop button and depending on the type of transmission:
- Automatic; when the drive selector is in the 'Park' position and the brake pedal is pressed.
- Manual; when the gear selector is in 'Neutral' and the clutch pedal is pressed.
COMPONENT DESCRIPTION
Immobilizer Antenna Unit
The IAU (immobilizer antenna unit) is used if the keyless vehicle module is unable to authorize the Smart Key. If the keyless vehicle module is unable to identify the Smart Key, for example if the Smart Key battery voltage is low or there is local RF interference, the transponder within the Smart Key can be read in the conventional manner. The driver will be alerted to this by a chime and a message in the instrument cluster message center 'SMART KEY NOT FOUND REFER TO HANDBOOK'.
Refer to Keyless Start Backup section.
Low Frequency Antenna
Six LF (low Frequency) antennas for the passive start system are positioned in specific locations within the vehicle.
The keyless vehicle module transmits an LF signal via the antennas which is received by the Smart Key. The Smart Key then responds by transmitting a RF (radio Frequency) signal which is received by the RF receiver and passed to the KVM (Keyless Vehicle Module) for authorization.
Keyless Vehicle Module
The keyless vehicle module controls signal transmissions to and from the Smart Key and provides authorization to allow the vehicle to be started. The module has a medium-speed CAN (controller area network) connection to the CJB (central junction box) for authorizing vehicle starting.
Radio Frequency Receiver
The RF (radio frequency) receiver transmission is received from the Smart Key to enable key identification.
CONTROL DIAGRAM
NOTE:
A = Hardwired connection; F = RF Transmission; N = Medium speed CAN bus; O LIN bus; W = LF Transmission; AH = Serial Communications Link
PRINCIPLES OF OPERATION
Passive Start
At the request of the CJB (central junction box) the KVM (Keyless Vehicle Module) prompts each of the internal low-frequency antennas to output a signal. When the Smart Key is in the vehicle cabin, it detects the low-frequency signals and responds with a RF radio frequency data-identification signal back to the KVM via the RF receiver.
If the data received matches that stored in the KVM it continues the passive start process by communicating a 'Smart Key valid' signal to the CJB (central junction box) via the medium-speed CAN (controller area network) bus.
Once the CJB (central junction box) receives the authorization and confirms the response with an internal calculation, it passes coded data to the ECM (engine control module) on the high-speed CAN (controller area network) bus. Upon confirmation from the ECM (engine control module) the ignition is enabled.
Before CJB (central junction box) sends a mobilization signal to the ECM (engine control module) it will exchange encrypted data with the electric steering lock mechanism to authorize unlocking of the steering column. The instrument cluster only provides a ground for the steering lock motor.
The CJB (central junction box) will enable the fuel pump relay which, on diesel vehicles operates the fuel pump and on gasoline vehicles sends a battery voltage supply to the fuel pump driver module to operate the fuel pump in conjunction with the ECM (engine control module).
NOTE:
If the KVM fails to locate the Smart Key, a message 'SMART KEY NOT FOUND REFER TO HANDBOOK' will appear in the instrument cluster message center and the keyless start back-up process will have to be used to mobilize and start the vehicle.
Keyless Start Backup
If the vehicle has been unlocked using the emergency key blade or the Smart Key is not detected by the vehicle, it will be necessary to use the keyless start backup to disarm the alarm and start the engine. The following process must be followed in this event:
- Position the Smart Key against the underside of the fascia, on the outboard side of the steering column, with the buttons facing downwards. This is the location of the IAU (immobilizer antenna unit).
- Holding the Smart Key in position and the brake / clutch pedal depressed, press the start/stop button to start the engine.
Smart Key positioned next to immobilizer antenna unit
This process bypasses the data exchange between the KVM and the CJB (central junction box); this is an inductive process and will operate if the battery in the Smart Key is discharged. A transponder within the Smart Key is detected by the IAU. The IAU confirms the code output from the transponder and communicates this code confirmation with the CJB (central junction box) via a LIN (local interconnect network) bus connection. The CJB (central junction box) then initiates the vehicle start process in the normal manner.