Lexus RX (RX 350L, RX450h) 2016-2022 Repair Manual: System Description

SYSTEM DESCRIPTION

GENERAL DESCRIPTION

The dynamic torque control AWD system detects the driving conditions based on signals from each ECU, switches, the steering sensor, the wheel speed sensor, and the acceleration sensor. The system controls the current passing through the 4WD linear solenoid of the electro magnetic control coupling sub-assembly, and performs electronic control to transfer the optimum torque to the rear wheels.

FUNCTION OF MAIN COMPONENTS

Component

Function

*1: w/ Optitron Meter Type

*2: w/ TFT Meter Type

Combination Meter Assembly

Multi-information display (AWD Warning)

Displays a warning to the driver when the system malfunctions.

AWD Lock Mode Indicator Light

  • Illuminates to inform the driver of the lock mode control status.
  • When lock mode is turned ON, the indicator light blinks twice and then remains illuminated.
  • When lock mode is turned OFF, the indicator light turns off.

Wheel Speed Sensors

Detect the wheel speed of each wheel.

Crankshaft Position Sensor

Detects the engine speed and outputs it to the ECM.

Throttle Position Sensor

Detects the throttle valve position and outputs it to the ECM.

Park/Neutral Position Switch Assembly

Detects the shift position of the transaxle and outputs it to the ECM.

Stop Light Switch Assembly

Detects when the brake pedal is depressed.

Steering Sensor

Detects the angle and direction of the steering wheel.

Acceleration Sensor (Airbag Sensor Assembly)*1

Acceleration Sensor (Yaw Rate Sensor Assembly)*2

Detects the vehicle's yaw rate.

Detects the vehicle's acceleration in the longitudinal and lateral directions.

Transfer

Transmits torque to the differential via the propeller shaft.

Rear Differential

Electro Magnetic Control Coupling Sub-assembly

- 4WD Linear Solenoid

Varies the distribution of torque in accordance with the current from the 4WD ECU assembly.

Electro Magnetic Control Coupling Sub-assembly

Varies the distribution of torque to the rear wheels in accordance with the current from the 4WD ECU assembly.

4WD ECU Assembly

Controls the current applied to the 4WD linear solenoid based on signals provided by the sensors in order to optimally distribute torque in accordance with driving conditions.

ECM

Outputs signals such as the shift position signal, throttle position signal, and crankshaft position signal to the 4WD ECU assembly.

Skid Control ECU (Brake Actuator Assembly)

Outputs signals such as the vehicle speed signal and stop light switch signal to the 4WD ECU assembly.

Main Body ECU (Multiplex Network Body ECU)

Outputs the parking brake switch signal to the 4WD ECU assembly via CAN communication.

AWD Lock Switch (Combination Switch Assembly)

Switches between auto mode and lock mode.

DRIVING FUNCTION

Control

Function

Starting Control

Controls the amount of torque to the rear wheels to ensure traction performance when starting off and to avoid the occurrence of tight corner braking phenomenon* when turning.

Normal Control

Controls the amount of torque to maintain stability while cornering and acceleration performance when accelerating straight ahead.

Reduces torque to the rear wheels when driving is judged to be stable to improve fuel consumption.

Control when Locked

Controls the amount of torque to the rear wheels to allow maximum traction performance.

Cornering Control

Uses pre-torque control, which is based on the drivers input, yaw rate feedback control and the vehicle status, to achieve excellent vehicle tracking while cornering.

Braking Control

When braking, cancels AWD to improve braking effectiveness.

VSC Cooperative Control

When suddenly accelerating during cornering on slippery surfaces, etc., the dynamic torque control AWD system and VSC function perform cooperative control which achieves smoother acceleration and higher stability.

Safety Control

Stops AWD control, transfers all torque to the front wheels, and warns the driver if a malfunction that could damage the drivetrain is detected in the dynamic torque control AWD system or other related systems.

  • *: Tight corner braking phenomenon: a phenomenon in which an AWD vehicle may lurch and decelerate due to a rotational speed difference between the front and rear wheels, such as during low-speed cornering in AWD mode.
    Parts Location
    PARTS LOCATION ILLUSTRATION *1 ECM *2 SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) *3 ELECTRO MAGNETIC CONTROL COUPLING SUB-ASSEMBLY - 4WD LINEAR SOLENOID *4 ENGINE ROOM RELAY BLOCK ...

    System Diagram
    SYSTEM DIAGRAM Communication Table Transmitting ECU Receiving ECU Signal Communication Method *1: w/ Optitron Meter Type *2: w/ TFT Meter Type Skid control ECU (Brake actuator asse ...

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    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

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