Adaptive Variable Suspension System (Diagnostics - Introduction): Other Lexus GS III facelift

PRECAUTION

Note. When there is a malfunction in the contact point of the terminals or installation problems with parts, removal and installation of the suspected problem parts may return the system to the normal condition either completely or temporarily. In order to determine the malfunctioning area, be sure to check the conditions at the time the malfunction occurred, sure as by DTC output and record it before disconnecting each connector or removing and installing parts. Since the Adaptive Variable Suspension system (AVS system) may be influenced by a malfunction in other systems, be sure to check for DTCs in the other systems. When removing and installing the absorber control ECU and each sensor, be sure to check that the normal display is output in Test Mode inspection and in DTC output inspection after installing all the parts. The CAN communication system is used for data communication between each of the ECUs and sensors. If there is trouble in the CAN communication line, the DTC of the communication line is output. If the DTC of the CAN communication line is output, repair the malfunction in the communication line and troubleshoot the AVS system. Since the CAN communication line has its own length and route, it cannot be repaired temporarily with a bypass wire, etc. While using the batteries for inspection, do not place the positive and negative tester probes too close to each other as a short circuit may occur. When disconnecting the negative (-) battery cable, initialize the following systems after the cable is reconnected. System See procedure Intuitive Parking Assist System Refer to INITIALIZATION Theft Deterrent System Refer to INITIALIZATION Variable Gear Ratio System Refer to INITIALIZATION

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1. SYSTEM DESCRIPTION Absorber Control ECU The shock absorber damping force can be switched individually for each of the four wheels using the information from the sensors, and the set mode can be selected, by operating the absorber control switch. Damping force switching controls are as follows: control according to vehicle speed, which is determined by driving conditions, anti-dive control, anti-squat control, rolling control, shudder control (Hinfinity control), which is controlled according to vehicle movement (road surface), bumpy control, and spring-bottom vibration control (unsprung damping control). Further, there is also a VSC cooperative control for VSC operations. Accurate damping force control is achieved by using nonlinear Hinfinity control based on the current theory in shudder control. The frequency of the bumps and shudders are monitored using signals from the acceleration sensor assembly, and the frequency of unsprung resonance is monitored using signals from the wheel speed sensors to achieve smooth damping control performance commensurate with driving status. Speed Sensor Control A smooth ride at low speed, and operability and stability at high speed, are balanced by making optimum settings of the damping force commensurate with vehicle speed, based on wheel speed sensor information. Anti-Dive Control The anti-dive control assures operability and stability, (smoothing dive due to speed changes during deceleration), by accurately controlling damping force commensurate with the chassis dive status detected during braking using speed signals from the wheels and signals from the stop light switch. Operability and stability during braking are assured while a smooth ride is also assured by setting the damping force to high both if deceleration G is great and when the driver has released the brake pedal. Anti-squat Control Vehicle squat is reduced, and operability and stability are assured, by accurately controlling the damping force by detecting vehicle squat during acceleration using the number of engine rotations. Rolling Control Excellent operability and stability during cornering are achieved by controlling the damping force commensurate with the level of the lateral acceleration calculated using the turning angle signals from the steering angle sensor and the vehicle speed signals from the wheel speed sensors. The outer damping force of the outer and inner turnings (for all four wheels independently) is controlled by using control theory according to the rolling control model for the absorbers (for roll suppression and bound suppression), which suppress movement in two directions from a virtual point on the inner turning, as described in the diagram below. That enables to achieve excellent operability and stability, and to assure turning and tracking performance and wheel-to-ground contact by optimizing the wheel status during rotation. Shudder Control (Hinfinity Control) If shudder in the roll and pitch directions is small, the shudder can be controlled by increasing the damping force for a specified time. If the shudder is great, the ride will lose its smoothness if the damping force only is properly increased. Consequently, to balance high damping performance and optimum ride smoothness, shudder control that applies the nonlinear Hinfinity control theory is used. Three acceleration sensor assemblies are used to detect sprung acceleration over road surface unevenness, and used to calculate the suspension stroke status by applying current control theory. The target damping force is calculated from these loads using Hinfinity control theory, and the damping force is then controlled for all four wheels independently. Damping control can be actively enhanced in the target frequency band by setting frequency weighting functions in the sprung acceleration in the shudder resonant frequency band. To control the sprung acceleration and vary the damping force to control the energy ratio of the sprung acceleration to the road surface input at the set value max. If the vehicle status is controlled by using shock absorber damping force only, and if the damping force varies greatly, shudder can easily occur in the sprung acceleration. Natural and smooth shudder control is achieved in the sprung damping, by applying nonlinear Hinfinity control theory. Bumpy Control If the frequency between the sprung resonance and unsprung resonance (bump frequency) is detected by using signals from the acceleration sensor while driving on a rough road surface in which shudder and bumps occur simultaneously, the damping force is set comparatively low, to achieve a smooth sensation within the vehicle, without the smooth ride being damaged. Spring-Bottom Vibration Control (unsprung damping control) If unsprung resonance is detected by using signals from the wheel speed sensors, the unsprung resonance is controlled by increasing the damping force for a fixed period to achieve high road surface contact without the smooth ride being damaged. VSC Operation Control (VSC cooperative control) The VDIM (VSC) effectiveness can be maximized by suitably switching the damping force commensurate with changes in the road surface μ and the vehicle lateral skid, using signals from the skid control ECU.
2. DAMPING FORCE CHARACTERISTICS Two kinds of mode, NORMAL and SPORT, can be selected by operating the absorber control switch. NORMAL is the mode that gives the highest priority to a comfortable ride. Damping force is lowest when driving under normal conditions. SPORT is the mode in which damping force is set higher, even when driving under normal conditions. SPORT improves further the driving performance and stability by utilizing wider area of high damping force, even when the damping force is affected by the driving and road conditions.
3. FAIL-SAFE FUNCTION When a failure occurs in the AVS (Adaptive Variable Suspension System) system, the absorber control indicator light comes on and AVS operation is prohibited.
4. DATA LIST/ACTIVE TEST Data list According to the DATA LIST displayed on Techstream, the value and status of the switch, sensor, ECU, etc. can be read without removing parts. Reading DATA LIST as the first step in troubleshooting is one way to shorten labor time. Active test Performing the ACTIVE TEST using Techstream allows the relay, ECU, etc. to operate without removing parts. Performing the ACTIVE TEST as the first step in troubleshooting is one way to shorten labor time.
5. FUNCTION OF COMPONENTS Components Function Absorber Control Switch (EMS Switch) Selects the damping force of the shock absorber (NORMAL or SPORT) Steering Angle Sensor Installed in the combination switch Detects the amount and direction of steering wheel movement and sends the signals to the skid control ECU via the CAN communication system Has a magnetic resistance element which detects the rotation of the magnet housed in the detection gear in order to detect changes of magnetic resistance and amount and direction of steering wheel movement Acceleration Sensor Assembly (Right Front) Detects the vehicle's vertical (right front) acceleration rate Houses absorber control ECU Acceleration Sensor Assembly (Left Front) Detects the vehicle's vertical (left front) acceleration rate Acceleration Sensor Assembly (Rear) Detect the vehicle's vertical (rear) acceleration rate Speed Sensor (Skid Control ECU) Sends the vehicle wheel speed signal, etc. to the absorber control ECU via CAN communication system Absorber Control Actuator Changes the damping force by reading the absorber control ECU signal Absorber Control ECU Determines the condition of the vehicle based on the signals received from the sensors and switch, and sends a control signal to the absorber control actuator Uses an internal acceleration sensor to detect the vehicle's vertical (right side) acceleration rate

FAIL-SAFE CHART

1. FAIL-SAFE FUNCTION When short circuit of the absorber control actuator is detected, the absorber control actuator located on the other side of the detected absorber will be set at step 9. The absorber control actuator remains at the step 9 position until the engine switch is turned off.
2. FAIL-SAFE CHART DTC No. Malfunction Item Fail-safe operation Fail-safe Cancellation Condition Indication C1715 C1716 C1717 Acceleration sensor circuit Shudder control (Hinfinity control) is cancelled Other controls are continued, setting the lowest step of the front and rear absorber control actuators at 9 The system returns to normal DTC: stored Indicator light: OFF C1725 C1726 C1727 C1728 Absorber control actuator circuit Control is cancelled (except malfunctioning area) after setting the step of the front and rear absorber control actuators at 9 The system returns to normal DTC: stored Indicator light: OFF C1761 Absorber control ECU Control is cancelled The system returns to normal DTC: stored Indicator light: OFF C1773 VGRS ECU Roll posture control is prohibited The system returns to normal DTC: stored Indicator light: OFF C1774 Power source circuit Control is cancelled The system returns to normal DTC: not stored Indicator light: OFF C1776 Wheel speed sensor circuit Control is cancelled after setting the step of the front and rear absorber control actuators at 9 The system returns to normal DTC: stored Indicator light: OFF C1777 Steering angle sensor circuit Roll posture control is prohibited The system returns to normal DTC: stored Indicator light: OFF U0100 CAN communication circuit Control is continued, setting engine rotation at 1000 rpm The system returns to normal DTC: not stored Indicator light: OFF U0101 CAN communication circuit Control is continued The system returns to normal DTC: not stored Indicator light: OFF U0122 CAN communication circuit Control is cancelled after setting the step of the front and rear absorber control actuators at 9 The system returns to normal DTC: not stored Indicator light: OFF U0126 CAN communication circuit Roll posture control is prohibited The system returns to normal DTC: not stored Indicator light: OFF U0130 CAN communication circuit Roll posture control is prohibited The system returns to normal DTC: not stored Indicator light: OFF U0132 CAN communication circuit Control is cancelled after setting the step of the front and rear absorber control actuators at 9 The system returns to normal DTC: not stored Indicator light: OFF