Anti-Theft - Passive
Anti-Theft - Passive
COMPONENT LOCATION
Anti-Theft - Passive:
INTRODUCTION
The Passive Anti-Theft System (PATS) prevents the vehicle from being driven away by unauthorized persons. This is achieved by having uniquely coded keys (both passive and transponder) and an encoded data exchange between multiple control modules. Unauthorized starting is prevented by inhibiting the fuel, engine (spark, injectors and crank) and ignition systems from operating.
The PATS is a function of the 'Passive Start' system. The system uses the following components:
- 'Smart Key'
- LF antennae - 3 off
- RF receiver
- Keyless vehicle module
- Start control module
- CJB
- ECM
- Instrument cluster.
The system is automatic and requires no input from the driver. The engine start system is initiated when the start/stop switch and the brake pedal are pressed simultaneously.
The engine management system will only allow engine crank, spark and injector functions when the following conditions are met:
- A hardwired Park/Neutral signal is received from the Transmission Control Module (TCM)
- A hardwired ignition signal is received from the CJB
- A hardwired crank request signal is received from the CJB
- Encrypted data exchange between the instrument cluster and the ECM is verified.
Before the CJB will send the hardwired ignition signal, it must satisfactorily complete the following:
- Exchange encrypted data with the keyless vehicle module to validate the smart key
- Exchange encrypted data with the instrument cluster to authorize the ignition status.
Additionally, before the CJB will send the hardwired crank request signal it must receive the following signals:
- Brake pressure signal from the ABS module which must be greater than a pre-determined threshold
- Hardwired transmission in 'Park' (P) signal from the selector lever.
START CONTROL MODULE
The start control module is located in the floor console, at the rear of the arm rest. The start control module 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 any reason, 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, PLEASE INSERT IN SLOT'. The Smart Key can be inserted into the start control module.
To insert the Smart Key, lift the arm rest on the floor console and slide back the spring loaded access cover on the start control module. Insert the Smart Key, with the key fob loop uppermost, into the slot. The start control module is motorized and will draw the Smart Key into the slot once inserted.
The start control module will then read the transponder within the Smart Key and, if the transponder identification is valid, pass authorization to the instrument cluster on the Local Interconnect Network (LIN) bus.
NOTE: Inserting the Smart Key into the start control module will not charge the Smart Key battery. The battery is nonchargeable and must be replaced with a new CR2032 battery if defective.
A message 'REMOVE SMART KEY' will be displayed if the Smart Key is still in the start control module and the driver's door is opened. The Smart Key can be removed by pushing downwards on the key fob loop and releasing. The start control unit motor will then drive the Smart Key out from the slot.
LF ANTENNA
Three Low Frequency (LF) antennae for the passive start system are positioned in specific locations in the vehicle. The LF antennae are positioned in the following locations:
- Behind center console, below heater assembly and audio modules.
- In floor console between the driver and passenger seats, below start control module.
- On the battery tray.
NOTE: On vehicles with the passive entry system, three additional antennae are used; one integrated into the rear bumper and one in each door handle assembly. These are only used by the passive entry system and have no function in the passive start system.
The keyless vehicle module transmits an LF signal via the antennae which is received by the Smart Key. The Smart Key then responds by transmitting a Radio Frequency (RF) signal which is received by the RF receiver and passed to the keyless vehicle module for authorization.
KEYLESS VEHICLE MODULE
The keyless vehicle module is located on the Right Hand (RH) 'A' pillar. The module controls signal transmissions to and from the Smart Key and provides authorization to allow the vehicle to be entered and started. The module has a medium speed Controller Area Network (CAN) connection to the Central Junction Box (CJB) for authorizing vehicle unlocking and starting.
RF RECEIVER
The RF receiver is located behind the overhead console. The receiver is available in two variants; 315 Mhz or 433 Mhz depending on market requirements. Transmissions are received from the Smart Key for key identification and remote lock/unlock requests or requests for operation of additional features.
CONTROL DIAGRAM
PRINCIPLES OF OPERATION
At the request of the CJB, the keyless vehicle module prompts each of the LF antennae to output a LF signal. When the Smart Key is within range, it detects the LF signals and responds with an RF identification signal. The RF signal is detected by the RF receiver and passed to the keyless vehicle module.
NOTE: The LF antenna located in the rear bumper and in each door handle are only fitted if the vehicle has the Passive Entry option.
The keyless vehicle module authorizes the Smart Key and passes this information to the CJB via the medium speed CAN bus. Once the CJB receives the authorization and confirms response with internal calculation, it passes the result to the instrument cluster on the medium speed CAN bus. Once the CJB receives the authorization and confirms the response, it allows the ignition to be activated when the start/stop switch is pressed.
On receipt of the authorization message, the instrument cluster initiates the unlocking of the electric steering column lock (if fitted). Once the electric steering column lock is unlocked and power has been removed, the instrument cluster will set its internal key status to valid. The instrument cluster will pass this key valid authorization to the auxiliary junction box. Once the auxiliary junction box receives the authorization and confirms the response with an internal calculation, it will enable the Fuel Pump Driver Module (FPDM).
The CJB also controls the engine crank request. If the transmission selector lever is in the park position and the driver presses the brake pedal and simultaneously presses the start/stop switch, the CJB interprets this as an engine crank request.
Before the engine crank request is allowed, the CJB compares a brake pressure signal received from the ABS module. The brake pressure signal is compared to an internally stored threshold value within the CJB. If the signal is greater than the stored threshold value, a crank request signal is sent to the ECM on the high speed CAN bus.
NOTE: If the Smart Key is not in the vehicle and an attempt is made to start the engine by pressing the start/stop switch, a message 'SMART KEY NOT FOUND, PLEASE INSERT IN SLOT' is displayed in the instrument cluster message center.
If the keyless vehicle module is unable to identify the Smart Key for any reason, the Smart Key can be inserted into the start control module. The start control unit will then read the transponder within the Smart Key and, if the transponder identification is valid, pass authorization to the instrument cluster on the Local Interconnect Network (LIN) bus.
If a replacement Smart Key is required, 2 Integrated Diagnostic System (IDS) diagnostic procedures are required to synchronize the passive start/entry and transponder functions of the Smart Key. If any module, which is involved in the Smart Key authorization process, require replacement, an IDS diagnostic procedure is also required to synchronize the replacement module into the system.