Toyota 4Runner: System Description

Toyota 4Runner Service Manual / Steering / Power Assist Systems / Power Steering System / System Description

SYSTEM DESCRIPTION

1. DESCRIPTION

(a) In the Variable Flow Control (VFC) power steering system, the power steering ECU assembly receives the steering angle signal, steering zero point memory, the steering speed, vehicle speed signal and engine speed signal through the CAN communication system. The power steering ECU assembly also controls the power steering solenoid valve mounted on the vane pump assembly in accordance with whether the vehicle is driving straight or turning in order to supply an appropriate power steering fluid volume.

Furthermore, without regard to whether or not the vehicle is being turned, if the power steering ECU assembly cannot receive the steering angle signal, steering zero point memory, vehicle speed signal or engine speed signal, the power steering warning light in the combination meter illuminates and the vehicle enters fail-safe mode. During fail-safe control, the resistance of the steering wheel increases drastically to inform the driver that the vehicle is in fail-safe mode.

2. FUNCTION OF MAIN COMPONENTS

Item	Function
Power steering warning light	Illuminates to inform the driver that a malfunction in the power steering system has occurred.
Power steering solenoid valve	Controls the power steering fluid volume by the control signals from the power steering ECU assembly.
Steering angle sensor	Transmits the steering angle signal and steering zero point memory to the power steering ECU assembly via CAN communication.
power steering ECU assembly	Processes the signals sent from master cylinder solenoid (skid control ECU), the steering angle sensor and ECM, and controls to the power steering solenoid valve.
Master cylinder solenoid (Skid control ECU)	Transmits the vehicle speed signal to the power steering ECU assembly via CAN communication.
ECM	Transmits the engine speed signal to the power steering ECU assembly via CAN communication.

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