Transmission Control Systems: Description and Operation

Previous automatic transaxle have selected each gear shift using the mechanically controlled throttle hydraulic pressure, governor hydraulic pressure and lock-up hydraulic pressure. The electronically controlled transmission, however, electrically controls the line pressure and lock-up pressure etc., through the solenoid valve. Engine control module control of the solenoid valve based on the input signals from each sensor, makes smooth driving possible by shift selection for each gear which is most appropriate to the driving conditions at that time.

1. GEAR SHIFT OPERATION
During driving, the engine control module selects the shift for each gear which is most appropriate to the driving conditions, based on input signals from the engine coolant temp. sensor to TERMINAL THW of the engine control module, and also the input signals to TERMINAL SPD of the engine control module from the speedometer devoted to the electronically controlled transmission. Current is then output to the electronically controlled transmission solenoid. When shifting to 1st speed, current flows from TERMINAL S1 of the engine control module to TERMINAL 3 of the electronically controlled transmission solenoid to GROUND, and continuity to the no.1 solenoid causes the shift.

For the 2nd speed, current flows from TERMINAL S1 of the engine control module to TERMINAL 3 of the electronically controlled transmission solenoid to GROUND, and from TERMINAL S2 of the engine control module to TERMINAL 1 of the electronically controlled transmission solenoid to GROUND, and continuity to solenoids no. 1 and no. 2 causes the shift.

For the 3rd speed, there is no continuity to no. 1 solenoid, only to no. 2, causing the shift.

Shifting into 4th speed (Overdrive) takes place when there is no continuity to both no. 1 and no. 2 solenoid.

2. LOCK-UP OPERATION
When the engine control module judges from each signal that lock-up operation conditions have been met, current flows from TERMINAL SL of the engine control module to TERMINAL 2 of the electronically controlled transmission solenoid to GROUND, and continuity to the lock-up solenoid performs the lock-up operation.

3. STOP LIGHT SW CIRCUIT
If the brake pedal is depressed (Stop light SW ON) when driving in lock-up condition, a signal is input to TERMINAL STP of the engine control module, the engine control module operates, and continuity to the lock-up solenoid is cut.

4. OVERDRIVE CIRCUIT
* Overdrive ON
When the O/D main SW is turned ON (O/D OFF indicator light turns OFF), a signal is input to TERMINAL OD2 of the engine control module, and engine control module operation causes gear shift when the conditions for overdrive are met.

* Overdrive OFF
When the O/D main SW is turned to OFF (O/D OFF indicator light turns ON), the current flowing through the O/D OFF indicator light flows through the O/D main SW to GROUND, causing the indicator light to light up. At the same time, a signal is input to TERMINAL OD2 of the engine control module, and engine control module operation prevents shift into overdrive.