Transmission Control Systems: Description and Operation

Previous automatic transmissions have selected each gear shift using mechanically controlled throttle hydraulic pressure, governor hydraulic pressure and lock-up hydraulic pressure. The Electronically Controlled Transmission, however, electrically controls the governor pressure and lock-up pressure through the solenoid valve. Control of the solenoid valve by the engine control module 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 SP2+ of the engine control module from the Vehicle Speed Sensor 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 1 of the Electronically Controlled Transmission solenoid to GROUND, and continuity to the No.1 solenoid causes the shift.
For 2nd speed, current flows from TERMINAL S1 of the Engine Control Module to TERMINAL 1 of the Electronically Controlled Transmission Solenoid to GROUND, and from TERMINAL S2 of the Engine Control Module to TERMINAL 2 of the Electronically Controlled Transmission solenoid to GROUND, and continuity to solenoids No.1 and No.2 causes the shift.
For 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 continuous to either No.1 or 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 3 of the Electronically Controlled Transmission solenoid to GROUND, causing continuity to the lock-up solenoid and causing 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 BK of the engine control module. The engine control module operates and continuous to the lock-up solenoid is cut.