Principles Of Operation

WARNING: This page is about a different car, the 2011 Jaguar XKR, 2011 Jaguar XK, 2010 Jaguar XKR, and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.

At the request of the central junction box (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 central junction box (CJB) via the medium speed controller area network (CAN) bus. Once the central junction box (CJB) receives the authorization and confirms response with internal calculation, it passes the result to the instrument cluster on the medium speed controller area network (CAN) bus. Once the central junction box (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 from the central junction box (CJB) the instrument cluster sets its internal key status to valid, then passes a key valid authorization message to the auxiliary junction box (AJB) on the medium speed controller area network (CAN) bus.

Once the auxiliary junction box (AJB) receives the authorization and confirms the response with an internal calculation, it enables the fuel pump driver module (FPDM).

The central junction box (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 central junction box (CJB) interprets this as an engine crank request.

Before the engine crank request is allowed, the central junction box (CJB) compares a brake pressure signal received from the anti-lock brake system (ABS) module. The brake pressure signal is compared to an internally stored threshold value within the central junction box (CJB). If the signal is greater than the stored threshold value, a crank request signal is sent to the engine control module (ECM) on the high speed controller area network (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, two procedures with a Jaguar approved diagnostic system are required to synchronize the passive start/entry and transponder functions of the Smart Key. If any module involved in the Smart Key authorization process is replaced, a diagnostic procedure is also required to synchronize the replacement module into the system.