Control Module: Description and Operation

Control System Diagram




Main Communication Signal






Line Pressure Control
- If the engine control unit sends the input torque signal equivalent to the engine driving force to the A/T control unit (TCM), the A/T control unit (TCM) controls line pressure solenoid.
- This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the driving plate.

Line Pressure System Diagram





Line Pressure Control Based On Line Pressure Characteristic Pattern Of A/T Control Unit (TCM)
- A/T control unit (TCM) has stored in memory a number of patterns for the optimum line pressure characteristics according to driving conditions.
- In order to obtain the most appropriate line pressure characteristic to meet the current driving state, the TCM controls the line pressure solenoid current valve and thus controls the line pressure.
- Normal line pressure control.
Each clutch is adjusted to the necessary pressure to match the engine drive force.




- Back-up control (Engine brake)
Line pressure according to speed is set during shift down by select operation while driving.




- During shift change
Set to line pressure that is necessary for shift change. Therefore, line pressure characteristic is set according to input torque and shift types.




- At low fluid temperature
When the A/T fluid temperature drops below the prescribed temperature, in order to speed up the action of each friction element, the line pressure is set higher than the normal line pressure characteristic.





Shift control
- The clutch pressure control solenoid is controlled by the signals from the switches and sensors. Thus the clutch pressure is adjusted to be appropriate to the engine load state and vehicle driving state. It becomes possible to finely control the clutch hydraulic pressure with high precision and a smoother shift change characteristic is attained.

Shift Control System Diagram




Shift description
Controls clutches with optimum timing and fluid pressure in response to engine speed, engine torque information, and etc.

Lock-up Control
Lock-up control is to enhance delivery efficiency by preventing the torque converter from slipping, engaging the lock-up piston into the torque converter.
It operates lock-up solenoid control in response to a signal from A/T control unit (TCM) and lock-up control valve behavior control, engages or releases the lock up piston of the torque converter.
Lock-up Operating Condition Table





Lock-up control valve control
- In the lock-up control valve, there is operating fluid pressure circuit linked into the lock-up piston and lock-up solenoid operates valve shift in response to a signal from the A/T control unit.
- Operating fluid pressure circuit that is applied to the lock-up piston chamber is controlled with the release or apply sides.

Lock-up Control System Diagram




Lock-up released
- In the lock-up control valve, there is operating fluid pressure circuit connected into the lock-up piston and lock-up solenoid operates valve shift in response to a signal from the A/T control unit.
Therefore, the lock-up piston is not coupled.
Lock-up applied
Smooth lock-up control
- A/T control unit (TCM) controls current value that is output to the lock-up solenoid when shifting lock-up applied state from lock-up released state.
Therefore the lock-up clutch is temporarily set to half-clutched state when shifting the lock-up applied state to reduce the shock.
- During the lock-up applied status, lock-up apply pressure is generated having the lock-up control valve to L/U by the lock-up solenoid.
Therefore, press the lock-up piston to be coupled.
Half-clutched state
- Changes current value that is output to the lock-up solenoid from A/T control unit (TCM) to gradually increase lock-up solenoid pressure.
In this way, the lock up apply pressure gradually rises and while the lock-up piston is put into half-clutched status, the lock-up piston operating pressure is increased and the coupling is completed smoothly.

Engine Brake Control
- The forward one-way clutch delivers driving force from the engine to the rear wheel but reverse driving from the wheel drive is not delivered since the one-way clutch is idling.
Therefore low coast brake solenoid is operated to prevent the forward one-way clutch from idling so that the engine brake is operated in the same as before.

Engine Brake Control System Diagram




- The operation of the low coast brake solenoid switches the low coast brake switch valve and controls the coupling and releasing of the low coast brake.
The low coast brake reducing valve controls the low coast brake coupling force.

Control Valve
Control Valve Functions






SUB ROM unit
1. Installing location: The valve body upper part
2. Function: To obtain A/T fluid pressure stability by compensating for solenoid&valve body unit fluid pressure differential.
3. Principle: Install additional ROM onto valve body of automatic transmission and input fluid pressure differential of solenoid &valve body so that TCM reads the input data to perform fluid pressure compensation.








4. Maintenance
(1) When replacing with a new TCM in the vehicle
A. TCM automatically reads SUB ROM DATA during I.G ON. At this time, shift range valve is off for about 2.5 second.
(2) When replacing A/T (regardless of new or old ones) in the vehicle
A. Must erase SUB ROM DATA stored in TCM.
B. Erase SUB ROM DATA in SCAN TOOL delete mode during shift stage in R-range + accelerator opening angle maintains 50% + I.G ON.
C. TCM reads SUB ROM DATA from a new A/T upon I.G ON again after I.G OFF.
(3) Moving TCM from vehicle A to another vehicle B
A. Perform the same way as in 2) above.