AIR SUSPENSION SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Pneumatic Cylinder with Shock Absorber Assembly Air Spring Portion Increases and decreases the vehicle height using compressed air.
    Integration Control and Panel Assembly Vehicle Height Adjustment Switch Enables the user to turn the vehicle height adjustment function on and off.
    Pneumatic Tank Assembly Pneumatic Tank Sub-assembly Stores compressed air required for vehicle height control.
    Height Control Pressure Sensor Detects the pressure in the tank.
    Height Control Way Height Control Pressure Sensor Detects the pressure in the pipe.
    No.2 Luggage Room R/B Suspension Control Relay Supplies power to the compressor motor.
    Compressor and Dryer Assembly No. 1 Height Control Compressor Compressor Motor Creates compressed air required for vehicle height control.
    Height Control Exhaust Valve Opens and discharges the compressed air in the system, including the compressed air in the pneumatic tank assembly and pneumatic cylinder with shock absorber assembly, to the outside air.
    Dryer Removes moisture from the compressed air created by the compressor motor.
    No. 3 Height Control Valve Sub-assembly Switches the airflow passages inside the system according to the control conditions.
    Height Control Compressor Thermistor Assembly Detects the temperature near the compressor motor.
    Height Control Filter Removes foreign matter when outside air is drawn into the system by the compressor motor.
    No. 1 and No. 2 Height Control Valve Sub-assembly Closes to maintain the compressed air in each pneumatic cylinder with shock absorber assembly. Also opens during vehicle height control to adjust the air volume in the pneumatic cylinder with shock absorber assembly.
    Height Control Sensor Sub-assembly Detects increases and decreases in the vehicle height.
    Suspension Control ECU Controls the vehicle height based on signals from each sensor, switch and ECU.
    Main Body ECU (Multiplex Network Body ECU)

    • Detects whether each door, luggage compartment door or hood is open or closed and sends signals to the suspension control ECU.

    • Detects whether the engine switch is on (IG), and sends signals to the suspension control ECU.

    • Detects the vehicle conditions (the parked condition and accessibility) and sends signals to the suspension control ECU.
    ECM

    • Detects the engine speed and sends signals to the suspension control ECU.

    • Detects whether the shift position, and sends signals to the suspension control ECU.
    Brake Actuator Assembly*1 Skid Control ECU Detects the wheel speeds, stop light switch condition, wheel cylinder pressure and master cylinder pressure, and sends signals to the suspension control ECU.
    Skid Control ECU Assembly*2 Detects the wheel speeds, stop light switch condition, wheel cylinder pressure and master cylinder pressure, and sends signals to the suspension control ECU.
    Yawrate Sensor (with Built-in Deceleration Sensor) Detects the vehicle's longitudinal and lateral acceleration and deceleration and sends signals to the suspension control ECU.
    Front Steering Control ECU*3 Detects the VGRS system operation condition and sends signals to the suspension control ECU.
    Engine Stop and Start ECU*4 Detects the stop and start system operation condition and sends signals to the suspension control ECU.
    Steering Sensor Detects the angle and direction of the steering wheel and sends signals to the suspension control ECU.
    Combination Meter Assembly High Mode Indicator Illuminates when High mode is turned on using the vehicle height adjustment function.
    Multi-information Display

    • Displays a message when a system malfunction occurs.

    • Enables the user to turn the vehicle height control on and off by vehicle height control off function.

    • Enables the user to turn the access mode control on and off by access mode control off function.

    • Enables the user to use the select parking height function to select whether High or Normal is used when the vehicle is parked.

    *1: Models with vacuum brake booster

    *2: Models without vacuum brake booster

    *3: Models with LDH system

    *4: Models with stop and start system

  2. OPERATING CONDITION


    1. Access Mode Control


      1. Ingress Height Control


        • The suspension control ECU determines whether a passenger is entering and increases the vehicle height when the following conditions are met.


          • A door unlock operation is performed using the entry unlock function.

          • A door unlock operation is performed and any door is opened without using the entry unlock function.

        Tech Tips

        The vehicle returns to its original height when the vehicle speed becomes 20 km/h or higher.

      2. Egress Height Control


        • The suspension control ECU determines whether a passenger is entering or exiting and increases the vehicle height when the following conditions are met.


          • The shift position is in P.

          • Any door is opened.

      3. Angle Adjustment Control when Doors Locked


        • When the following conditions are met, the suspension control ECU controls the vehicle height and adjusts the vehicle angle according to the change that occurs when passengers exit the vehicle.


          • The engine switch is off.

          • All doors are closed.

          • A door lock operation is performed.

  3. SYSTEM CONTROL


    1. The suspension control ECU controls the vehicle height based on signals from each sensor, switch and ECU.

      B0056QVC01
      *1 Suspension Control ECU *2 Suspension Control Relay
      *3 Height Control Pressure Sensor *4 Pneumatic Tank Assembly
      *5 Compressor Motor *6 Height Control Exhaust Valve
      *7 Dryer *8 No. 3 Height Control Valve Sub-assembly
      *9 No. 1 and No. 2 Height Control Valve Sub-assembly *10 Height Control Sensor Sub-assembly
      *11 Pneumatic Cylinder with Shock Absorber Assembly *12 Vehicle Height Adjustment Switch
      *a CAN communication line - -

      1. The air in the pneumatic tank assembly is supplied to the pneumatic cylinder with shock absorber assembly when a vehicle height increase operation is performed.


        • During ingress height control of the access mode control, the airflow passage indicated by the dotted line is used to improve the vehicle height increase adjustment speed.

        B0056KNC01
        *1 No. 3 Height Control Valve Sub-assembly *2 Height Control Pressure Sensor
        *3 Pneumatic Tank Assembly *4 Compressor Motor
        *5 Dryer *6 Height Control Exhaust Valve
        *7 No. 1 and No. 2 Height Control Valve Sub-assembly *8 Pneumatic Cylinder with Shock Absorber Assembly
        *a Raised - -

      2. When a vehicle height decrease operation is performed, the compressor motor is operated to return the air in the pneumatic cylinder with shock absorber to the pneumatic tank assembly.

        B00567SC01
        *1 No. 3 Height Control Valve Sub-assembly *2 Height Control Pressure Sensor
        *3 Pneumatic Tank Assembly *4 Compressor Motor
        *5 Dryer *6 Height Control Exhaust Valve
        *7 No. 1 and No. 2 Height Control Valve Sub-assembly *8 Pneumatic Cylinder with Shock Absorber Assembly
        *a Lowered - -

      3. Access Mode Control


        • The access mode control is performed only when the access mode control off function is turned on via the multi-information display.


        • Ingress Height Control


          • The suspension control ECU determines if a passenger is entering according to the conditions of the door locks and doors. When High mode of the vehicle height adjustment function is off, the suspension control ECU increases the height at the front and rear of the vehicle by 30 mm (1.18 in.). When High is selected via the select parking height function, the suspension control ECU increases the vehicle height by 20 mm (0.79 in.). When High mode is turned on via the vehicle height adjustment function, the suspension control ECU increases the vehicle height by 10 mm (0.39 in.).

          • The vehicle returns to its original height when the vehicle speed becomes 20 km/h (12 mph) or higher. After that, vehicle speed-sensitive control is performed. When High mode is turned on via the vehicle height adjustment function, the vehicle returns to the height for High mode.

        Tech Tips


        • The ingress height control can always be canceled via the vehicle height adjustment switch. At that time, the vehicle height is returned to the condition before ingress height control was performed.

        • When the engine is not started with ingress height control canceled, ingress height control can be resumed by operating the vehicle height adjustment switch again.

        • When the engine has started up with ingress height control canceled, High mode can be turned on and off by operating the vehicle height adjustment switch again.

        • Ingress height control is resumed when the vehicle speed becomes 20 km/h (12 mph) or higher.

        B00569TE02

        • Egress Height Control


          • The suspension control ECU determines if a passenger is entering or exiting according to the shift position and door conditions and increases the height of the front and rear of the vehicle by 10 mm (0.39 in.).

          • The vehicle returns to its original height when the vehicle speed becomes 20 km/h (12 mph) or higher. After that, vehicle speed-sensitive control is performed.

        Tech Tips


        • Egress height control operates only when High is selected via the select parking height function.

        • Egress height control does not operate even when High mode is turned on using the vehicle height adjustment function.

        • The egress height control can always be canceled via the vehicle height adjustment switch. At that time, the vehicle height is returned to the condition before egress height control was performed.

        • When the engine is not started with egress height control canceled, egress height control can be resumed by operating the vehicle height adjustment switch again.

        • When the engine has started up with egress height control canceled, High mode can be turned on and off by operating the vehicle height adjustment switch again.

        • Egress height control is resumed when the vehicle speed becomes 20 km/h (12 mph) or higher.

        B00567GE02

        • Angle (Left/Right) Adjustment Control when Doors Locked


          • When the suspension control ECU detects that a door lock operation is performed, it adjusts the vehicle angle according to the change that occurs when occupants exit the vehicle.

      4. Auto Leveling Control


        • Auto leveling control is performed when the engine has started up to maintain thevehicle height at a certain level regardless of the number of passengers and load capacity.

        Tech Tips

        Auto leveling control for when the vehicle is parked is as follows.

        Vehicle Condition When Vehicle Height Increases due to Passengers Exiting Vehicle or Other Reasons When Vehicle Height Increases due to Passengers Entering Vehicle or Other Reasons.
        During ingress height control of access mode control X* X*
        During egress height control of access mode control (when Normal selected via select parking height function) X* ○
        During egress height control of access mode control (when High selected via select parking height function) X* ○
        Access mode control off X* ○

        ○: Operates

        X: Does not operate

        *: Control is performed when the vehicle speed becomes 20 km/h or more.

      5. Vehicle Speed-sensitive Control


        • The vehicle height is automatically adjusted according to the vehicle speed. When the vehicle speed increases, the vehicle height is decreased. On the other hand, when the vehicle speed decreases, the vehicle height is increased.

          B00569EE02

    2. When the suspension control ECU detects system pressure decreases and increases, accumulation control and pressure decrease control are performed to adjust the pressure in the system.


      1. Accumulation Control


        • When the height control pressure sensor installed on the pneumatic tank assembly detects a decrease in the system pressure, the compressor motor is operated to draw air in from outside the vehicle and accumulate it in the pneumatic tank assembly.

        • The compressor motor repeatedly operates and stops at certain intervals to protect the motor from overheating.

        • To discharge moisture in the dryer from the exhaust valve, a certain amount of air is drawn in and discharged so that a constant pressure is maintained.

        Tech Tips


        • Accumulation control is normally performed when the vehicle is traveling. However, if the pressure in the system is extremely low, accumulation control is performed even when the vehicle is stopped. Vehicle height control does not operate when the pressure is extremely low.

        • When the system pressure is low and the wheel height control sensors detect that the vehicle height is decreased, the compressed air from the compressor motor is directly sent to the pneumatic cylinder with shock absorber assemblies. In that case, the adjustment speed becomes slower than normal.

      2. Pressure Decrease Control


        • When the height control pressure sensor installed on the pneumatic tank assembly detects that the system pressure is high, the compressed air in the pneumatic tank assembly is discharged from the exhaust valve to the outside air.

        Tech Tips


        • When the system pressure is high and the vehicle height is decreased, the compressed air in the pneumatic cylinder with shock absorber assembly is directly discharged from the exhaust valve to the outside air. In that case, the adjustment speed becomes slower than normal.

  4. FUNCTION


    1. Vehicle Height Control Off Function


      1. Vehicle height control can be turned on and off by operating the multi-information display.

    2. Access Mode Control Off Function


      1. The access mode control can be turned on and off by operating the multi-information display.

    3. Select Parking Height Function


      1. High or Normal can be selected for the parked vehicle height by operating the multi-information display.

      2. When High is selected, this function increases the vehicle height by 10 mm higher than the normal height via egress height control of the access mode control to maintain the vehicle height even while the vehicle is parked.

    4. Vehicle Height Adjustment Function


      1. High mode can be turned on and off by operating the vehicle height adjustment switch. When High mode is turned on, the vehicle height is increased by 20 mm (0.79 in.) more than the normal level, and the high mode indicator in the combination meter assembly illuminates.

        Tech Tips

        Switching operations are possible only when the engine has started up.

  5. FAIL-SAFE


    1. The fail-safe function operates when a system malfunction occurs. At this time, the master warning light in the combination meter assembly illuminates, a message is displayed on the multi-information display and the buzzer sounds to inform the driver of a system malfunction.

  6. DIAGNOSIS


    1. In order to make system inspections easier to perform, a diagnosis function is used in consideration of serviceability. Refer to the Repair Manual for details of the diagnosis function.