Lexus RX300 (MCU15). Service manual — part 48

CHASSIS — U140F AUTOMATIC TRANSAXLE

CH

BO

161ES22

Sleeve

Solenoid Coil

Spool Valve

Hydraulic
Pressure

Current

!

"

65

2. Solenoid Valves

Solenoid Valves SL1, SL2 and SLT

1) General

In order to provide a hydraulic pressure that is proportion to current that flows to the solenoid coil, the
solenoid valve SL1, SL2 and SLT linearly controls the line pressure and clutch and brake engagement
pressure based on the signals it receives from the engine & ECT ECU.
The solenoid valves SL1, SL2 and SLT have the same basic structure.

2) Functions of Solenoid Valve SL1, SL2 and SLT

Solenoid

Action

Function

SL1

For clutch and brake engagement pressure
control

D B

1

brake pressure control

D Lock-up clutch pressure control

SL2

control

C

2

clutch pressure control

SLT

For line pressure control

D Line pressure control

D Secondary pressure control

CHASSIS — U140F AUTOMATIC TRANSAXLE

181CH12

161ES65

Control Pressure

Line
Pressure

Solenoid Valve ON

Drain

Solenoid Valve OFF

161ES23

Solenoid Valve S4

B

3

Accumulator

Line Pressure

S4 OFF

S4 ON

3-4 Shift Valve

Except 4th

B

3

Brake ON

C

3

4th

C

3

Clutch ON

B

3

C

3

Accumulator

#

#

66

Solenoid Valves S4 and DSL

1) General

The solenoid valves S4 and DSL use a three-way solenoid valve.

2) Function of Solenoid Valve S4

The solenoid valves S4 when set to ON controls the 3-4 shift valve to establish the 4th by changing
over the fluid pressure applied to B

3

brake and C

3

clutch.

CH

BO

CHASSIS — U140F AUTOMATIC TRANSAXLE

181CH13

Solenoid Valve DSL

Lock-up Relay Valve

“R”

Lock-up ON Chamber

Secondary Pressure

Lock-up OFF Chamber

“R”

“L”

C

2

Lock Valve

B

2

Control Valve

B

2

181CH14

Input Turbine
Speed Sensor

Counter Gear
Speed Sensor

67

3) Function of Solenoid Valve DSL

The solenoid valve DSL controls the B

2

control valve via the C

2

lock valve when the transaxle is shifted

in the R or L position.
During lock-up, the lock-up relay valve is controlled via the C

2

lock valve.

3. Fluid Temperature Sensor

A fluid temperature sensor is installed inside the valve body for direct detection of the fluid temperature.

4. Speed Sensors

The U140F automatic transaxle has adopted an input turbine speed sensor (for the NT signal) and a counter
gear speed sensor (for the NC signal). Thus, the engine & ECT ECU can detect the timing of the shifting
of the gears and appropriately control the engine torque and hydraulic pressure in response to the various
conditions.

CHASSIS — U140F AUTOMATIC TRANSAXLE

68

JAUTOMATIC TRANSAXLE CONTROL SYSTEM

1. General

The automatic transaxle control system of the U140F automatic transaxle consists of the controls listed
below.

System

Function

Clutch Pressure Control

D Controls the pressure that is applied directly to B

1

brake and C

2

clutch

by actuating the shift solenoid valve in accordance with the engine &
ECT ECU signals.

D The solenoid valves SL1 and SL2 minutely controls the clutch pressure

in accordance with the engine output and driving conditions.

Apply Orifice Control

The apply orifice control valve varies the apply orifice to control the flow
volume supplied to the B

3

brake.

Centrifugal Fluid Pressure
Cancelling Mechanism

Applies an equal pressure from the opposite side to cancel the influence
of the pressure that is created by centrifugal force.

Line Pressure Optimal
Control

Actuates the solenoid valve SLT to control the line pressure in accordance
with information from the engine & ECT ECU and the operating
conditions of the transaxle.

Snow Mode Control

The snow mode control enables the driver to select the snow mode switch
which allows the vehicle to start in 2nd gear.

Engine Torque Control

Retards the engine ignition timing temporarily to improve shift feeling
during up or down shifting.

Shift Timing Control

The engine & ECT ECU sends current to the solenoid valve SL1 and/ or
SL2 based on signals from each sensor and shifts the gear.

Lock-Up Timing Control

The engine & ECT ECU sends current to the shift solenoid valve based
on signals from each sensor and engages or disengages the lock-up clutch.

“N” to “D” Squat Control

When the shift lever is shifted from “N” to “D” range, the gear is
temporarily shifted to 3rd and then to 1st to reduce vehicle squat.