Lock-Up Control

AUTOMATIC GEARBOX - JATCO

DESCRIPTION AND OPERATION

44-43

Operation

General
The EAT ECU controls the following functions:

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Gear shift scheduling

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Lock-up control

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Line pressure control

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Driving mode engagement

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Sport mode engagement

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Manual (CommandShift) mode engagement

l

Reverse inhibit

l

Hill mode strategy engagement

l

Downhill recognition

l

Cruise mode engagement

l

Cooling strategy engagement

l

Selector position display

l

Driving mode display

l

Fault status

l

Fault code storage

l

Emergency/Fail-safe program control.

Gear Shift Scheduling
The EAT ECU uses the relationship between the vehicle speed and the throttle position to carry out gear shift 
scheduling. Depending on these inputs, the EAT ECU controls gear selection using the three shift solenoid valves 
located in the valve block.

Lock-Up Control
The EAT ECU monitors the relationship between vehicle speed and throttle position to calculate when to lock-up the 
torque converter.

Lock-up control is possible in 4th and 5th gears. For example, lock-up is possible at high speed cruising with low 
throttle position. Torque converter lock-up is also provided in 2nd and 3rd gears when high fluid temperatures are 
detected by the ECU.   

A refinement to the torque converter lock-up system is the reduction of harshness or shock during torque converter 
lock-up.

The EAT ECU controls the lock-up solenoid valve to provide a smooth lock-up function. The solenoid is operated 
slowly, and gradually varies the fluid pressure to the lock-up control valve. This causes the lock-up clutch to engage 
slowly, producing a smooth operation.

To promote engine warm-up at low temperatures, the EAT ECU will inhibit lock-up if the gearbox fluid temperature is 
below 40

°

C (104

°

F).