Transmission Control Systems: Description and Operation

System Outline

Previous automatic transaxle have selected each gear shift using mechanically controlled throttle hydraulic pressure, governor hydraulic pressure and lock up hydraulic pressure. The electronically controlled transmission, however, controls the line pressure and lock up pressure etc. electrically, through the solenoid valve. The engine control module controls each solenoid valve based on the input signals from each sensor, which makes smooth driving possible by shift selection for each gear that 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 vehicle speed sensor devoted to the electronically controlled transmission. Current is then output to the electronically controlled transmission solenoid. When shifting to 1st speed, the current flows from TERMINAL S1 of the engine control module to TERMINAL 3 of the solenoid to GROUND, and from TERMINAL S2 of the engine control module to TERMINAL 6 of the electronically controlled transmission solenoid to GROUND, and continuity to the No.1 and No.2 solenoid causes the shift.

For 2nd speed, the current flows from TERMINAL S1 of the engine control module to TERMINAL 3 of the solenoid to GROUND, and from TERMINAL S2 of the engine control module to TERMINAL 6 of the 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 continuity to both No.1 and No.2 solenoid.

2. 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.

3. Overdrive Circuit

- Overdrive on
When the engine is turned on from ignition off, the engine control module turns the O/D on. When the O/D main SW is pushed while the O/D is off, a signal is input into TERMINAL ODMS of the engine control module, and the O/D is turned on by the engine control module. In this case, the engine control module controls the gear shift according to the vehicle's driving condition, using the O/D range. At this time, the O/D off indicator light is off.

- Overdrive off
When the O/D main SW is pushed while the O/D is on, a signal is input into TERMINAL ODMS of the engine control module, and the O/D is turned off. At this time, the current flows through the O/D off indicator light to TERMINAL ODLP of the engine control module. As a result, the O/D off indicator light turns on, and the engine control module controls the gear shift according to the vehicle's driving condition, without using the O/D range.