Transmission Control Systems: Description and Operation

A140E AUTOMATIC TRANSAXLE (ECT) [3S-GE]

WHAT IS THE ECT?

(ECT) means Electronic Controlled Transaxle. The hydraulic control system of the previous automatic transaxle has been changed, the throttle and governor pressure have been replaced by electronic signals and a micro computer has been used to give precise control of shift timing and lock-up timing.

FEATURES OF THE ECT

a. The shift pattern can be chosen.
In the ECT ECU micro computer used in the A14OE, two types of shift pattern, Power and Normal, are recorded in the memory. By operating the pattern select switch, the driver can select the preferred shift pattern.

b. Reduced fuel consumption and reduced shock during shifting is made possible.

Precise control of the shift timing by the ECT ECU, operation of the lock-up clutch from low speeds, and decreased fuel consumption are made possible. Also, shock during shifting is reduced.

c. Self-Diagnostic System.
When a malfunction occurs in the electronic control system, the driver is informed of this fact. Also, there is a Self-Diagnostic System which displays the location of the malfunction when the service connector is shorted.

d. Fail-Safe System.
A Fail-Safe System is included so that, even if a malfunction occurs in the electronic control system, the vehicle will be able to operate.

A140-E CONSTRUCTION AND OPERATION

When the A140E (ECT) (3S-GE models) is compared with the A14OL (3S-FE models), the automatic transaxle body has the same construction and operation, with the exception of the hydraulic control system, as the A140L.

The electronic control system, which controls the shift timing and lock-up timing, has been added.

1. HYDRAULIC CONTROL SYSTEM (Comparison with the A14OL)

VALVE BODY - Additions or changes to solenoid valve
In the A14OE there are three solenoid valves, the No. 1, the No. 2 and the lock-up solenoid valves. Shifting occurs according to whether the No. 1 and No. 2 solenoid valves are ON or OFF, and the lockup solenoid valve controls the lock-up clutch.

GOVERNOR VALVE - Removed
With the A140E, the governor valve has been replaced with a speed sensor, so that instead of the governor pressure, a speed sensor signal is sent to the ECT ECU.





SHIFT CONTROL IN ECT
1. The vehicle speed is sensed by the vehicle speed sensor, which sends this data to the ECU in the from of electrical signals.
2. The angle to which the throttle is open is sensed by the throttle position sensor, which sends this data to the ECU in the form of electrical signals.
3. The ECT computer determines the shift point on the basis of these two signals and operates the solenoid valves in the hydraulic control unit, thus shifting the transmission.





2. ELECTRONIC CONTROL SYSTEM





COMPONENTS
The electronic control system for controlling the shift timing and the operation of the lock-up clutch is composed of the following three parts:

a. Sensors: These sense the vehicle speed and throttle position and send this data to the ECT ECU in the form of electronic signals.

b. ECT ECU: This determines the shift and lock-up timing based upon the signals from the sensors.

c. Actuators: Solenoid valves divert hydraulic pressure from one circuit of the hydraulic control unit to another, thus controlling shifting and lock-up timing.