Electronic Power Steering System (Diagnostics - Introduction): Overview Lexus GS III рестайлинг

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1. NOTICE FOR INITIALIZATION NOTE: If the cable of the negative (-) battery terminal has been disconnected, initialize the following systems when the cable is reconnected. System Name See procedure Variable Gear Ratio Steering System Refer to «INITIALIZATION»(ref-386951-S21829001392011022400000) Intuitive Parking Assist System Theft Deterrent System
2. HANDLING PRECAUTIONS When handling the electronic parts: Avoid any impact to electronic parts such as ECUs and relays. Replace these parts with new ones if dropped or subjected to a severe blow. Do not expose any electronic parts to high temperature or humidity. Do not touch the connector terminals in order to prevent deformation or malfunctions due to static electricity. If the power steering ECU assembly has been replaced with a new one, initialize the rotation angle sensor and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-387136-S12158804652011022400000) . When handling the power steering link assembly: Avoid any impact to the power steering link assembly, especially to the motor or torque sensor. Replace with new parts if dropped or subjected to a severe blow. Do not pull on the wire harness when moving the power steering link assembly. If the power steering link assembly has been replaced with a new one, clear the rotation angle sensor calibration value, initialize the rotation angle sensor, and calibrate the torque sensor zero point. Refer to «CALIBRATION»(ref-387136-S12158804652011022400000) . If replacing the power steering link assembly, perform VGRS actuator angle initialization. Refer to «INITIALIZATION»(ref-386975-S05283496462011022400000) and VGRS actuator angle neutral calibration. Refer to «CALIBRATION»(ref-386975-S06876666312011022400000) after wheel alignment adjustment. When disconnecting and reconnecting the connectors: Turn the power switch ON (IG), center the steering wheel, and turn the power switch OFF again before disconnecting the connectors related to the electronic power steering system. Ensure that the power switch is off before reconnecting the connectors related to the electronic power steering system. After reconnection, center the steering wheel and turn the power switch ON (IG). NOTE: Do not turn the power switch ON (IG) when the steering wheel is not centered. If the above operations are not carried out properly, the steering center point (zero point) will deviate, which may lead to a difference in steering effort between turning the steering wheel to the left and right. If there is a difference in steering effort between turning the steering wheel to the left and right, perform steering zero point calibration. Refer to «CALIBRATION»(ref-387136-S12158804652011022400000) .
3. PRECAUTIONS FOR CAN COMMUNICATION CAN communication is used to receive information from the skid control ECU, steering control ECU, absorber control ECU, ECM and steering angle sensor, and to transmit warnings to the combination meter. It is also used for communication between terminals TC and TS of the DLC3. If there are any problems in the CAN communication lines, DTCs indicating communication line malfunctions are output. Perform troubleshooting for communication line problems if CAN communication DTCs are output. Be sure to start troubleshooting on the electronic power steering system only when data communication is normal. Temporary fixing or repairing with bypass wiring, etc. is impossible because the length and path of each CAN communication line cannot be changed.
4. BUS LINE REPAIR After repairing the bus line with solder, wrap the repaired part with vinyl tape. NOTE: The CANL bus line and CANH bus line must be installed together all the time. When installing, make sure to twist them. CAN bus lines are likely to be influenced by noise if the bus lines are not twisted. The difference in length of the CANL bus line and CANH bus line should be within 100 mm (3.937 in.). Leave approximately 80 mm (3.150 in.) loose in the twist near the connector. Do not use bypass wiring between the connectors. NOTE: The feature of the twisted wire harness will be lost if you use bypass wiring.

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HINT

Transmitted when the vehicle detects different levels of friction between the tires and road surface due to road conditions.

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1. DESCRIPTION The EPS system generates assist torque to assist steering effort through the operation of the motor installed on the power steering link assembly. The direction and amount of power assistance are determined by signals from the torque sensor, and controlled in accordance with vehicle speed. As a result, steering effort is controlled to be light during low speed driving and moderately heavy during high speed driving.
2. FUNCTIONS OF COMPONENTS Components Function Power Steering ECU Calculates degree of assistance needed based on steering torque and vehicle speed. Drives the motor based on motor electric angle obtained from the motor rotation angle sensor. Boosts battery voltage to generate motor drive voltage. Restricts power assistance to protect the system if the motor and ECU overheat. Torque Sensors Detect steering effort generated when the steering wheel is turned. Power Steering Motor Located coaxially with the rack shaft. Its rotation is converted to the rectilinear motion of the steering rack via the ball screw nut and ball. Motor Rotation Angle Sensor Detects motor rotation angle.
3. OPERATION EXPLANATION The torque sensors are mounted on the input shaft to the main shaft and on the output shaft to the pinion shaft. The input and output shafts are joined by a torsion bar. If the steering wheel is turned, the torsion bar twists, resulting in a difference in the rotation angle detected by each torque sensor. The power steering ECU calculates torque based on this difference. The power steering ECU calculates proper assisting torque, according to vehicle speed, based on the torque obtained the previous step. Then the ECU controls the motor drive circuit in order to cause it to generate assisting torque. A ball screw nut is attached to the motor shaft. It converts the rotational motion of the motor into the rectilinear motion of the steering rack via the ball. The assisting force generated in the above process will reduce the steering effort required by the driver.