Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Telematics Control Module (TCU)

Telematics Control Module (TCU)

  1. Battery cover
  2. Battery pack
  3. Battery tray
  4. Electrical connector
  5. GPS antenna connector
  6. GSM antenna connector
  7. Telematics Control Module

The TCU is located in the right rear corner of the luggage compartment, behind the trim panel.

For security reasons the TCU is located in a position that is not easy to access. This deters the action of a thief to remove or disconnect the module. Ease of disconnection would disable the tracking facility.

The TCU controls the Telematics system, communicating with the vehicle systems over high speed CAN powertrain systems bus and the medium speed CAN body systems bus. The system transmits/receives signals via Radio Frequency (RF), Global Positioning System (GPS) and GSM.

The Telematics Control Module has an integral embedded Subscriber Identification Module (SIM) card. The embedded SIM card is part of the module circuitry and cannot be removed. The embedded SIM card is configured to enable the network to retrieve and pass information to the Telematics Service Provider (TSP), this enables the TSP to call back the Telematics Control Module. During an eCall and bCall, the embedded SIM card will be used, overriding the SIM card in the SIM Card Reader. This will result in loss of WiFi during the call and call back.

A battery back-up pack, consisting of two battery cells, is integrated into the TCU. The battery pack enables continued operation in the event of a vehicle main power source dis-connection; for example in a major accident or in the case of deliberate action of a thief as part of a vehicle theft attempt. This feature enables the eCall and vehicle tracking functions to carry on operating in the above mentioned circumstances.

Telematics Control Module Battery Pack

Telematics Control Module Battery Pack

The battery pack is located in the TCU, under a cover which is retained by a screw.

The battery pack contains one re-chargeable cell and one non-rechargeable cell. The two battery cells are controlled separately by the TCU software.


The two battery cells cannot be replaced as separate items. The battery pack is replaced as a complete unit.

The use of two different battery cells provides continued performance at very low temperatures. The re-chargeable cell cannot deliver the charge effectively at very low temperatures. The non-rechargeable cell has improved performance at low temperatures.

The back-up battery will only be active during an eCall, bCall or stolen vehicle tracking session in which the vehicle power supply is disabled. Once the non-rechargeable cell has been used it will require replacement to restore the full capability of the eCall and stolen vehicle tracking systems.

TCU battery back-up power is also required for the Land Rover logistics tracking system when the vehicle is in transit mode.

Transit mode removes power to the TCU approximately 15 seconds after the ignition is switched off (power mode 0). The ignition off mode may occur before the TCU has sent all of its logistics tracking data to the manufacturer servers.

The backup battery enables the TCU to reliably deliver this data. The TCU is programmed not use the non-rechargeable cell for this purpose.

The TCU is in a pre-activated state when in transit mode. The nonrechargeable battery function is not activated as it would become depleted during transportation to the dealer and would immediately require a service replacement before handing the vehicle over to the customer. For this reason only the re-chargeable cell is used in these circumstances.

During the vehicle PDI (pre-delivery inspection) process the TCU is removed from transit mode and switched on to an 'activated state' where both battery cells become active. During a TCU main power source disconnection the re-chargeable battery cell will always be used first. The nonrechargeable cell is only used if eCall or stolen vehicle tracking are activated.

The expected battery pack life is approximately 10 years if not used frequently.

The TCU charges the re-chargeable cell when the ignition is on (power mode 6). The charging function is controlled and regulated by the TCU software.

If either battery cell becomes depleted below a preset threshold or fails completely the following warnings/actions are displayed in the message center:

  • SOS System Limited
  • SOS System Not Available.

A signal is sent to the Telematics Service Provider and a Diagnostic Trouble Code (DTC) is set in the TCU.

When the back-up battery has been replaced, the system must be re-set using a specific application on a Land Rover approved diagnostic system, setting the battery level back to 100%.

Service Mode

Before disconnecting power to the TCU, for example disconnecting the primary vehicle battery to carry out maintenance repairs, the vehicle owner must place the TCU into 'Service Mode'.

If the disconnection procedure is not carried out, the system will activate the InControl Secure application and will enter 'Theft Notification' or 'Stolen Vehicle Tracking' mode during which time the charge in the back-up battery would be used. If the non-rechargeable back-up cell becomes depleted through this action, it may reach the point where it requires replacing.

For security purposes 'Service Mode' is the sole responsibility of the vehicle owner.

During vehicle maintenance, where the primary vehicle battery is disconnected for a period of time exceeding the 10 hour window, the vehicle owner must either be informed by the dealer to re-activate Service Mode (using their mobile phone app) or the owner must inform the 'Stolen Vehicle Tracking' service provider that the vehicle is currently in the dealership for repairs with the vehicle battery disconnected, instructing the service provider to ignore the Stolen Vehicle Tracking notifications during the repair period.

Service Mode

Transport Mode

The TCU contains a motion sensor which is used for vehicle movement detection as part of the stolen vehicle tracking system. Prior to transporting the vehicle, for example a ferry journey, the vehicle owner must place the TCU into 'Transport Mode' to disable the motion sensor.

If the motion sensor is not disabled and the ignition is switched off (power mode = 0), but vehicle movement is detected, the 'Theft Notification' function will be activated. As with Service Mode, Transport Mode is the sole responsibility of the vehicle owner for security reasons.

The motion sensor is capable of detecting slow movement, e.g. jacking the vehicle to remove a road wheel, or winching onto a transporter.

Triggering of the sensor does not immediately generate a 'Theft Notification', but it will activate the GPS receiver and measure the vehicle's movement. If the vehicle moves more than a predefined distance (approximately 200 meters) the TCU sends a theft alert to the service provider.

The service provider contacts the vehicle owner to determine if a genuine theft has taken place. If a vehicle theft is confirmed the service provider initiates full GPS tracking of the vehicle.

Transport Mode disables the movement assessment by the GPS that follows a motion detection, therefore no 'Theft Notification' will be sent to the service provider. Should transporting the vehicle exceed the 10 hour window it is the responsibility of the vehicle owner to reset Transport Mode to avoid a false theft notification being generated.

Transport Mode

When the vehicle has the ignition off (power mode 0) and the MultiCAN buses are 'asleep', the TCU is still active, enabling movement detection should an illegal attempt be made to move the vehicle. The TCU has a permanent battery feed to enable this function. The drain on the vehicle primary battery is minimal and the vehicle remains well within its quiescent drain target.

The TCU is linked to the engine immobilization circuit. When a start request is made the Central Junction Box (CJB) requests the TCU to pass a secure identification over the MultiCAN bus. If the identification matches the one in the CJB, the start request is authorised.

In the event of disconnection or damage to the roof pod or the telematics antenna, resulting in the loss of the GSM signal, an internal antenna, integrated into the TCU, is used as a back-up GSM antenna. The backup GSM antenna is used to re-establish communication with the emergency service provider or TSP.


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