Lexus SC300 / Lexus SC400. Service manual - part 93

1. 

FUNCTION OF COMPONENTS

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

OPERATION

2. 

HYDRAULIC CONTROL SYSTEM
The hydraulic control system is composed of the oil pump, the valve body, the solenoid valves, the accumu-
lators, the clutches and brakes, as well as the fluid passages which connect all of these components.
Based on the hydraulic pressure created by the oil pump, the hydraulic control system governs the hydrau-
lic pressure acting on the torque converter clutch, clutches and brakes in accordance with the vehicle driv-
ing conditions.
There are 4 solenoid valves on the valve body.
The No.1 and No.2 solenoid valves are turned on and off by signals from the ECM to operate the shift
valves, and change the gear shift position.
The No.3 solenoid valve is operated by signals from the ECM to engage or disengage the lock–up clutch
of the torque converter clutch.
The No.4 solenoid valve is operated by signals from the ECM to control the engagement speed and reduce
gear shift shock.

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

OPERATION

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3. 

ELECTRONIC CONTROL SYSTEM
The electronic control system for the A340E automatic transmission provides extremely precise control of
the gear shift timing and lock–up timing in response to driving conditions as sensed by various sensors
located throughout the vehicle and in response to the engine’s running condition.
At the same time, the ECM control reduces vehicle squat when the vehicle starts out and gear shift shock.
The electronic control system is also equipped with a self diagnosis system which diagnoses malfunctions
of electronically controlled components and warns the driver, and a fail–safe system which makes it pos-
sible for the vehicle to continue functioning when a malfunction occurs.

CONSTRUCTION

The electronic control system can be broadly divided onto 3 groups; the sensors, ECM and actuators.

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

OPERATION

SYSTEM DIAGRAM

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

OPERATION

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