Transmission Control Module

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.

The transmission control module (TCM) outputs signals to control the shift control solenoid valve and the EPRS to control the hydraulic operation of the transmission.

The transmission control module (TCM) processes signals from the transmission speed and temperature sensors, the engine control module (ECM) and other vehicle systems. From the received signal inputs and pre-programmed data, the module calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.

The engine control module (ECM) supplies the engine management data over the high speed controller area network (CAN) bus. The transmission control module (TCM) requires engine data to efficiently control the transmission operation, for example; flywheel torque, engine speed, accelerator pedal angle, engine temperature. The steering angle sensor and the anti-lock brake system (ABS) module also supply data to the transmission control module (TCM) on the high speed controller area network (CAN) bus. The transmission control module (TCM) uses data from these systems to suspend gear changes when the vehicle is cornering and/or the anti-lock brake system (ABS) module is controlling braking or traction control.

Using the signal inputs and the memorized data, the transmission control module (TCM) control program computes the correct gear and torque converter lock-up clutch setting and the optimum pressure settings for gear shift and lock-up clutch control. Special output-side modules (power output stages, current regulator circuits), allow the transmission control module (TCM) to control the solenoid valves and pressure regulators and consequently precisely control the hydraulics of the automatic transmission. In addition, the amount and duration of engine interventions are supplied to the engine management by way of the controller area network (CAN) bus.

The transmission has a fully electronic JaguarDrive selector with no Bowden cable connection to the transmission. The transmission selections are made using a rotary JaguarDrive selector which rises from the floor console once the engine is running. Rotation of the JaguarDrive selector to any of the five positions is sensed by the transmission control module (TCM) via the high speed controller area network (CAN) bus. The transmission control module (TCM) then reacts according to the selected position. The 'S' (sport) position selection allows the transmission control module (TCM) to operate the transmission using the semi-automatic 'Jaguar Sequential Shift'.

Gear selections are sensed by the transmission control module (TCM) when the driver operates the steering wheel paddle switches. Once the JaguarDrive selector position is confirmed, the transmission control module (TCM) outputs appropriate information on the high speed controller area network (CAN) bus.

If the JaguarDrive selector is in 'D', 'Jaguar Sequential Shift' is temporary and will cancel after a time period or can be cancelled by pressing and holding the + paddle for approximately 2 seconds.

If the JaguarDrive selector is in 'S', 'Jaguar Sequential Shift' is permanent and can only be cancelled by pressing and holding the + paddle for approximately 2 seconds or by moving the JaguarDrive selector to the 'D' position.

The transmission control module (TCM) can be reprogrammed using an approved Jaguar diagnostic system using a flash code. The transmission control module (TCM) processor has a 440 kb internal flash memory. Of this capacity, approximately 370 kb are used by the basic transmission program. The remainder, approximately 70 kb is used to store vehicle-specific application data.

Engine Stall

If the vehicle stalls it will coast down in gear, with the transmission providing drive to the engine. A restart can be attempted at this point and the engine may start and the driver can continue.

If the coast down speed reduces such that the speed of the engine is less than 600 rev/min, the transmission will go to neutral, D illumination will flash in the instrument cluster. The driver needs to select neutral or park and then press the brake pedal to restart the engine.

If the start/stop button is pressed when driving, the message ENGINE STOP BUTTON PRESSED is displayed in the message center but there will be no change to the ignition state. If the driver requires to switch off the engine, the start/stop button must be pressed for a second time. The engine will be stopped and will be back driven by the transmission as the vehicle coasts down. When the engine speed is less than 600 rev/min the transmission engages neutral (flashing D illumination in the instrument cluster). When vehicle speed is less than 2 km/h (1.2 mph) Park is engaged. The JaguarDrive selector automatically rotates back to its lowered P position and the vehicle ignition is switched off.

The park engagement is prevented in a stall case as the ignition power is on and D was the last selected gear. The park engagement speed at ignition off is from the least value of the wheel speeds (controller area network (CAN) signal) and transmission output speed (internal signal).