Automatic gearbox - Jatco (Driving Modes): Description and operation

Driving Modes

There are five different driving modes that the driver can select: l Normal mode l Sport mode l Manual (Steptronic) mode l Hill Descent Control (HDC) mode l Cruise mode.

Normal, sport, cruise and HDC modes are selected manually by the driver. Fast off and stop go modes are controlled by the EAT ECU responding to driving conditions.

The different modes are selected by the gear selector lever or, in the case of cruise mode and HDC, a separate switch. The gear change scheduling is altered to correspond with the mode selected.

Normal Mode On power up the EAT ECU always initialises normal mode. In this mode all automatic/adaptive modes are active. Normal mode uses gear shift and lock-up maps which allows vehicle operation which is a compromise between performance, fuel consumption and emissions.

Sport Mode In sport mode the EAT ECU controls the gearbox to downshift more readily and use gear change schedules that hold the lower gears for longer at high engine speeds. This enhances acceleration and vehicle responsiveness. Sport mode is selected by moving the gear selector lever to the 'S/M' position. 'Sport' is displayed in the instrument pack LCD when this mode is selected.

Manual (Steptronic) Mode Manual mode allows the driver to operate the gearbox as a semi-automatic, Steptronic gearbox. The driver can change up and down the five gears with the freedom of a manual transmission.

Gearshift maps programmed in the EAT ECU protect the engine at high engine speeds by automatically changing up to prevent engine over speed and changing down to prevent stalling.

Manual mode is entered by moving the selector lever to the 'S/M' position and then moving the lever to either the + or - positions to move the gearbox up and down the five gear ratios. Manual mode is exited by moving the selector back to position 'D'.

HDC Mode The HDC mode assists the ABS in controlling the descent of the vehicle in either 1st gear ratio or reverse gear ratio. HDC mode is initiated by selecting 1 or R on the selector lever, depressing the HDC button adjacent to the selector lever and throttle pedal released (low demand position). The instrument pack illuminates the HDC warning lamp and the LCD will display the selected gear (1 or R).

The EAT ECU will maintain the selected gear ratio and apply engine braking to assist the ABS in controlling the vehicle's descent.

Cruise Mode Cruise control is activated by depressing the cruise control switch in the centre console. When cruise control is active, the EAT ECU senses this as a hardwired input from the cruise control ECU (non NAS KV6 models) or interface unit (Td4 and NAS KV6 models). In cruise mode the EAT ECU uses a dedicated gearshift map to control the gearbox and assist in maintaining the set vehicle speed. The gearbox cruise mode is cancelled by applying the brake pedal or deselecting cruise control. Cruise mode is suspended when the throttle demand is increased and is reinstated when the pedal is released and the set speed resumed. Cruise mode is also suspended when the suspend switch on the steering wheel is pressed.

Reverse Inhibit

If the vehicle exceeds 6 mph (10 km/h) in the forward direction, and Reverse (R) gear is selected, the EAT ECU switches on the low clutch timing solenoid valve in the valve block, which drains the fluid from the reverse clutch.

This function prevents the gearbox from engaging reverse gear when the vehicle is moving in a forward direction, so preventing damage to the gearbox.