System Outline

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 line pressure, throttle pressure, lock-up pressure and accumulator pressure etc., through the solenoid valve. The electronically controlled transmission is a system which precisely controls gear shift timing and lock-up timing in response to the vehicle's driving conditions and the engine condition detected by various sensors, making smooth driving possible by shift selection for each gear which is the most appropriate to the driving conditions at that time, and by preventing downing, squat and gear shift shock When starting off.

1. GEAR SHIFT OPERATION
When driving, the engine warm up condition is input as a signal to TERMINAL THW of the engine control module from the engine coolant temp. sensor and the vehicle speed signal from vehicle speed sensor is input to TERMINAL SP2+ of the engine control module. At the sane time, the throttle valve opening signal from the throttle position sensor is input to TERMINAL VTA1 of the engine control module as throttle angle signal.

Based on these signals, the engine control module selects the best shift position for the driving conditions and sends current to the electronically controlled transmission solenoid.

When shifting to 1st speed, the current flows from TERMINAL S1 of the engine control module --> TERMINAL 4 of electronically controlled transmission solenoid --> GROUND, and continuity to No.1 solenoid causes the shift (no.2 solenoid does not have continuity at this time).

For 2nd speed, the current flows simultaneously from TERMINAL S2 of the engine control module --> TERMINAL 8 of electronically controlled transmission solenoid --> GROUND, and from TERMINAL S1 of the engine control module --> TERMINAL 4 of electronically controlled transmission solenoid --> GROUND, and continuity to No.1 and No.2 solenoids causes the shift.

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

Shifting into the 4th speed (overdrive) occurs when no current flows to No.1 and No.2 solenoids, the No.4 solenoid (for accumulator back pressure modulation) is installed to adjust the back pressure on the accumulator and control the hydraulic pressure during shifting and lock-up in order to provide smooth shifting with little shift shock.

2. LOCK-UP OPERATION
When the engine control module decides, based on each signal, that the lock-up condition has been met, the current flows through TERMINAL SLU+ of the engine control module --> TERMINAL 3 of electronically controlled transmission solenoid --> TERMINAL 7 --> TERMINAL SLU- of the engine control module --> GROUND, so continuity to no.3 solenoid (for lock-up) causes lock-up.

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 nodule operates and cuts the current to the solenoid to release lock-up.

4. OVERDRIVE CIRCUIT
When the transmission control SW detects that the shift lever is shifted into "D" position, the current flows from GAUGE fuse --> TERMINAL 4 of the A/T indicator light SW (park/neutral position SW) --> TERMINAL 9 --> TERMINAL 2 of the transmission control SW --> TERMINAL 3 --> TERMINAL C-1 of the combination meter TERMINAL A-16 --> GROUND.
When the transmission control SW detects that the shift lever is shifted into "3" position, the current flows from GAUGE fuse --> TERMINAL 4 of the A/T indicator light SW (park/neutral position SW) --> TERMINAL 9 --> TERMINAL 2 of the transmission control SW --> TERMINAL 1 --> TERMINAL C-2 of the combination meter TERMINAL A-16 --> GROUND.



5. ELECTRONICALLY CONTROLLED TRANSMISSION PATTERN SELECT SW CIRCUIT
When the electronically controlled transmission pattern select SW is changed from "NORM" to "PWR", the current through the GAUGE fuse flows to TERMINAL A-4 or B-1 of electronically controlled transmission pattern select SW --> TERMINAL A-3 or B-2 --> TERMINAL PWR of the engine control module. At the same time, the current flows to TERMINAL A-1 of the Combination Meter --> TERMINAL A-10 --> TERMINAL PWRL of the engine control module -->GROUND. And the engine control module performs shift up and shift down at a higher vehicle speed range compared with "NORM" position.