AUTOMATIC TRANSAXLE SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Shift Solenoid Valve SL1 Controls the No. 1 clutch (C1) pressure.
    Shift Solenoid Valve SL2 Controls the No. 2 clutch (C2) pressure.
    Shift Solenoid Valve SL3 Controls the No. 3 clutch (C3) pressure.
    Shift Solenoid Valve SL4 Controls the No. 4 clutch (C4) pressure.
    Shift Solenoid Valve SL5 Controls the No. 1 brake (B1) pressure.
    Shift Solenoid Valve SL6 Controls the No. 2 brake (B2) pressure.
    Shift Solenoid Valve SLT (Line Pressure Control Solenoid Assembly)
    • Controls line pressure.

    • Switches the sequence valve.

    Shift Solenoid Valve SLU (Lock-up Control Solenoid Assembly)
    • Controls the lock-up clutch pressure.

    • Switches the pressure relay valve.

    Shift Solenoid Valve SL Switches the lock-up relay valve.
    Transmission Revolution Sensor (NT) Detects the input speed of the transaxle.
    Transmission Revolution Sensor (NC) Detects the speed of the counter gear.
    ATF Temperature Sensor (Transmission Wire) Detects the ATF temperature.
    Accelerator Pedal Sensor Assembly Detects the accelerator pedal opening angle.
    Throttle Body with Motor Assembly Throttle Position Sensor Detects the throttle valve opening angle.
    Mass Air Flow Meter Sub-assembly Air Flow Meter Detects the intake air volume and intake air temperature.
    Intake Air Temperature Sensor
    Crank Position Sensor Detects the engine speed and performs the cylinder identification.
    Engine Coolant Temperature Sensor Detects the engine coolant temperature.
    Park/Neutral Position Switch Assembly Detects the shift lever position.
    Transmission Floor Shift Assembly Transmission Control Switch
    • Detects when the shift lever is in S.

    • Detects the shift-up and shift-down operations performed by the driver when the shift lever is in S.

    Shift Paddle Switch (Transmission Shift Switch Assembly)*1 Detects the shift-up and shift-down operations performed by the driver.
    Electric Parking Brake Switch Assembly Drive Mode Select Switch*2 Selects the drive mode (ECO, NORMAL, SPORT).
    Steering Pad Switch Assembly Cruise Control Switch Turns the cruise control system on and off, and conducts various operations including vehicle speed setting, acceleration, deceleration and control cancellation.
    Stop Light Switch Assembly Detects when the brake pedal is depressed.
    ECM
    • Controls engine output and each shift solenoid valve in response to a signal from each sensor and switch.

    • Makes a diagnosis and memorizes the failed section when the ECM detects a malfunction.

    Air Conditioning Amplifier Assembly Transmits various air conditioning state signals to the ECM.
    Airbag Sensor Assembly
    • Detects the vehicle's longitudinal and lateral acceleration.

    • Detects the vehicle's yaw rate.

    Millimeter Wave Radar Sensor Assembly*3 Sends the information about the operation conditions of the dynamic radar cruise control system to the ECM.
    Combination Meter Assembly Malfunction Indicator Lamp (MIL) Illuminates to inform the driver when the ECM detects a malfunction.
    Multi-information Display
    • Displays the shift lever position.

    • Displays the shift range.

    • Displays the drive mode.*2

    Buzzer Sounds when the shift-down operation is rejected.

    *1: Models with shift paddle switch (transmission shift switch assembly)

    *2: Models with drive mode select switch

    *3: Models with dynamic radar cruise control system

  2. SYSTEM CONTROL


    1. The electronic control system of the UA80E automatic transaxle uses the controls listed below.

      Control Outline
      Shift Timing Control The ECM sends current to shift solenoid valves SL1, SL2, SL3, SL4, SL5, SL6, and/or SLU, based on signals from various sensors, in order to shift the gears.
      Clutch to Clutch Pressure Control
      • Controls the pressure that is applied directly to the C1, C2, C3, C4 clutches and B1, B2 brakes by actuating the shift solenoid valves (SL1, SL2, SL3, SL4, SL5 and SL6) in accordance with signals from the ECM.

      • The solenoid valves SLT, SLU, SL, SL1, SL2, SL3, SL4, SL5 and SL6 precisely control the clutch pressure in accordance with the engine output and driving conditions.

      Line Pressure Optimal Control Actuates shift solenoid valve SLT to control the line pressure in accordance with information from the ECM and the operating conditions of the transaxle.
      Lock-up Control
      • The ECM sends current to shift solenoid valves SL and SLU based on signals from various sensors to engage or disengage the lock-up clutch.

      • Controls shift solenoid valve SLU, provides an intermediate mode between the on and off states of the lock-up clutch, and increases the operating range of the lock-up clutch to improve fuel economy.

      Powertrain Cooperative Control Controls both shift control and engine output control in an integrated way, achieving excellent shift characteristics and driveability.
      Deceleration Downshift Control To prevent engine speed from decreasing and thereby maintain fuel cut, the ECM performs downshifts before fuel cut ends.
      Direct Connected Down Shift When the accelerator pedal is depressed, the vehicle downshifts smoothly through the intermediate gears to the selected gear, without delay of drive force or engine speed increase.
      Artificial Intelligence Shift Control (AI-shift Control)
      • Based on the signals from various sensors, the ECM determines the road conditions and the intention of the driver. Thus, an appropriate shift pattern is automatically determined, improving driveability.

      • When the SPORT mode is selected, the shift pattern changes according to driver intention to make dynamic driving possible.*1

      Multi-mode Automatic Transmission
      • When the shift lever is moved to S, driving in a gear position selected using the shift lever or shift paddle switch (transmission shift switch assembly)*2 is enabled.

      • Operating the shift paddle switch (transmission shift switch assembly) "-" with the shift lever in D enables D (fixed range mode).*2

      • The ECM appropriately controls the automatic transaxle in accordance with the range selected while in D (fixed range mode).*2

      Drive Mode Select*1 Drive mode (NORMAL, ECO, SPORT) switching is performed via drive mode select operation.
      Fail-safe If a malfunction is detected in the sensors or solenoids, the ECM performs fail-safe control to prevent vehicle driveability from being significantly affected.
      Diagnosis When the ECM detects a malfunction, the ECM records the malfunction and memorizes the information that relates to the fault.

      *1: Models with drive mode select switch

      *2: Models with shift paddle switch (transmission shift switch assembly)

    2. Clutch Pressure Control


      1. The ECM monitors the signals from various types of sensors, such as the transmission revolution sensor (NT) and transmission revolution sensor (NC), allowing the linear solenoid valves SLT, SL1, SL2, SL3, SL4, SL5, SL6 and SLU to precisely control the clutch pressure in accordance with engine output and driving conditions. As a result, the transmission has smooth shift characteristics.

        B0082T8E01
    3. Clutch-to-Clutch Pressure Control


      1. Clutch-to-Clutch pressure control is used for shift control. As a result, shift control in 2nd gear or above is possible without using a one-way clutch, making the automatic transaxle lightweight and compact.

      2. Using the fluid pressure circuit, which enables the clutches and brakes (C1, C2, C3, C4, B1 and B2) to be controlled independently, and the high flow SL1, SL2, SL3, SL4, SL5, and SL6 linear solenoid valves, which directly control the clutch pressure, the ECM controls each clutch and brake accordingly with the optimum fluid pressures and timings in accordance with the information transmitted by the sensors, and then shifts the gears. As a result, the transmission has highly responsive and excellent shift characteristics.

        B00833AE03
    4. Line Pressure Control


      1. The line pressure is controlled using shift solenoid valve SLT.

      2. Through the use of shift solenoid valve SLT, the line pressure is optimally controlled in accordance with the engine torque information, as well as with the internal operating conditions of the torque converter clutch assembly and the automatic transaxle assembly.

      3. Accordingly, the line pressure can be accurately controlled in accordance with the engine output, traveling condition, and the ATF temperature, thus realizing smooth shift characteristics and optimizing the workload of the oil pump (reducing parasitic losses).

        B0082SUE01
    5. All Range Lock-up


      1. Compared to the previous model, the UA80E performs lock-up control at lower speeds as well as at higher opening angles, enabling direct transmission of power similar to a manual transmission. Furthermore, the increased rate of engagement contributes to improved fuel efficiency.

      2. By increasing the lock-up range, and suppressing engine revving, smooth driving with high responsiveness and linearity is realized.

        B0082O5E01
        *1 UA80E L/U Range
        *2 Accelerator Pedal Angle
        *3 Conventional A/T
        *4 Vehicle Speed
        B0082R2E01
      3. Previously, lock-up was cancelled when downshifting to avoid shift shock, but with a torque converter adopting a multiple disc lock-up clutch as well as precision control taking into account transient characteristics of engine torque and hydraulic pressure, it has become possible to maintain lock-up continuously.

      4. In 1st gear and the low engine speed regions of 2nd and higher gears, lock-up is not performed, and the torque converter function is employed to realize smooth driving.

        Gear Position Shift Lever Position
        D,S
        1st X
        2nd ○*(During acceleration)
        3rd ○*
        4th ○*
        5th ○*
        6th ○*
        7th ○*
        8th ○*

        ○: Operates

        X: Does not operate

        *: Except at low engine speed range

    6. Powertrain Cooperative Control


      1. At low accelerator opening angles, the highly efficient low engine speed ranges are aggressively employed, contributing to improved fuel efficiency and reduced noise.

      2. Previous driving force characteristics were dependent on the torque characteristics of the engine electronic throttle opening angle and the gear ratio at each gear speed level. To achieve the driver's target driving force, the new control system uses an independent engine torque request for each gear, realizing increased fuel efficiency and driveability.

      3. At low accelerator opening angle ranges, highly efficient engine ranges are aggressively employed, realizing increased fuel efficiency. At the same time the differences between target driving forces at each gear level are small, enabling smooth downshift without noticeable driving force change.

      4. When the accelerator is deeply depressed to accelerate, the target driving force is set to be directly linked to the engine speed change, resulting in a direct and energetic feeling of acceleration, with the goal of achieving high balance of fuel efficiency and driveability.

        B0082VWE01
        *1 Drive Force
        *2 Engine Speed
        *3 Accelerator Pedal Angle
    7. Deceleration Downshift Control


      1. The ECM performs downshift control to help prevent the engine speed from decreasing, thus keeping fuel cut control operating for as long as possible. In this way, fuel economy is improved.

      2. In this control, the transmission downshifts from 7th to 3rd before fuel cut control ends when the vehicle is decelerated in the 8th gear, so that fuel cut control continues operating.

        B0082VFE01
    8. Direct Connected Downshift


      1. Smooth vehicle acceleration changes and linear changes in engine speed during downshifting were realized.

      2. By precisely controlling hydraulic pressure, downshifting from a high gear to a low gear is accomplished with a smooth shift through the intermediate gears without any unevenness of engine speed or drive force.

        B0082Y0E01
        *1 Conventional A/T
        *2 Accelerator Pedal Angle
        *3 Engine Speed
        *4 Vehicle's Acceleration Forces
    9. Artificial Intelligence Shift Control (AI-shift Control)


      1. The automatic transaxle gear is determined by the shift pattern, which uses the vehicle speed and throttle valve opening angle.

      2. Also, when SPORT mode is selected, the system switches to a shift pattern which frequently uses a low shift position selected according to the vehicle acceleration and unnecessary shift changes are suppressed. Therefore, vehicle stability is achieved and vehicle acceleration is improved.

      3. Additionally, AI-shift control enables the ECM to estimate the road conditions and the driver's intention in order to automatically control the shift pattern in the optimal manner. As a result, a comfortable ride has been achieved.

      4. The AI-shift control includes road condition support control and driver's intention support control.

      5. The AI-shift control determines optimal transaxle control based on input signals and automatically changes the shift pattern.

        B0082YWE14
      6. Under road condition support control, the ECM determines the throttle opening angle and the vehicle speed in addition to whether the vehicle is being driven uphill or downhill. To achieve optimal drive force while driving uphill, this control prevents unnecessary upshifts. To achieve the optimal engine braking while driving downhill, this control automatically performs downshifts.

        B0082W8E17
      7. The ECM, without the need of the shift pattern select switch used in the conventional models, estimates the driver's intention based on the accelerator operation and vehicle operating conditions to select a shift pattern that is well-suited to each driver.

    10. Multi-mode Automatic Transmission


      1. When the shift lever is moved to S, the system changes from automatic shift control to S mode control, where the driver can manually change the gear position by moving the shift lever or operating the shift paddle switch (transmission shift switch assembly)* to the "+" (upshift) and "-" (downshift) sides.

        *: Models with shift paddle switch (transmission shift switch assembly)

      2. On models with a shift paddle switch (transmission shift switch assembly), when automatic shift control is performed with the shift lever in D, D-range paddle active control is performed by shift paddle switch (transmission shift switch assembly) operation. The driver can select the desired shift range by operating the shift paddle switch (transmission shift switch assembly) to the "+" (upshift) and "-" (downshift) sides.

      3. When the vehicle is being driven at a speed that is higher than the maximum safe speed for a downshift, any attempt to shift to a lower range by operating the shift lever will not be performed. This is done in order to protect the automatic transaxle. In this case, the ECM sounds the buzzer in the combination meter assembly twice to alert the driver.

        B00832PE01
      4. The driver can select S mode by moving the shift lever to S. At this time, the 4th or 5th or 6th shift range will be selected according to the vehicle speed (During AI-shift control, however, the 3rd shift range may be selected).

      5. Under this control, the ECM performs optimal shift control within the usable gear range that the driver selects. As with an ordinary automatic transaxle, it shifts to 1st gear when the vehicle is stopped.

      6. The shift lever position and the shift range are indicated by the shift position indicator in the combination meter assembly (The shift range is shown only when the S mode control or D-range paddle active control*).

        *: Models with shift paddle switch (transmission shift switch assembly)

      7. Holding the shift lever toward "+" with the shift lever in S will change the shift range to the S8 range regardless of the current range (S1 to S7).

      8. In order to prevent excessive engine speed, a function was adopted that automatically selects a higher shift range before engine speed becomes too high.

      9. In order to protect the automatic transmission, a function is adopted that automatically selects a higher shift range when the fluid temperature is high.

        Usable Gear Chart:
        Shift Range Shift Position Indicator Usable Gear
        S8 8 1st to 8th
        S7 7 1st to 7th
        S6 6 1st to 6th
        S5 5 1st to 5th
        S4 4 1st to 4th
        S3 3 1st to 3rd
        S2 2 1st to 2nd
        S1 1 1st
      10. D-range Paddle Active Control (Models with Shift Paddle Switch (Transmission Shift Switch Assembly))


        1. When the shift lever is in D, D-range paddle active control operates according to shift paddle switch (transmission shift switch assembly) operation and the system enters shift range selection mode. Shift paddle switch (transmission shift switch assembly) is provided on the back of the steering wheel to allow engine brake force control and downshift operations for acceleration to be performed while gripping the steering wheel.

        2. The initial range when D-range paddle active control starts is determined according to the last gear position before shift paddle switch (transmission shift switch assembly) operation.

          Initial Range when Control Starts
          Gear Position before Shift Paddle Switch (Transmission Shift Switch Assembly) Operation Initial Range after Shift Paddle Switch (Transmission Shift Switch Assembly) "-" (Downshift) Operation Initial Range after Shift Paddle Switch (Transmission Shift Switch Assembly) "+" (Upshift) Operation
          1st D1 D1
          2nd D1 D2
          3rd D2 D3
          4th D3 D4
          5th D4 D5
          6th D5 D6
          7th D6 D7
          8th D7 -
        3. Normal driving automatically resumes (automatic shift control) in the following conditions:

          Normal Driving (Automatic Shift Control) Recovery Conditions
          Situation Condition
          Vehicle Stop 1 second after the vehicle stops, normal driving (automatic shift control) resumes.
          Shift Paddle Switch (Transmission Shift Switch Assembly) "+" (Upshift) Operation Operate and Hold for 1 Second or More When operated and hold for 1 second or more, normal driving (automatic shift control) resumes.
          Continuous Accelerator Pedal Depression D1 In order to prevent continuous driving at high loads caused by forgetting to switch from D-range paddle active control to normal driving (automatic shift control), when the accelerator pedal is continuously depressed for 3 seconds or more, normal driving (automatic shift control) resumes.
          D2
          D3
          D4
          D5
          D6
          D7
  3. FUNCTION


    1. Drive Mode Select (Models with Drive Mode Select Switch)


      1. The motive force characteristics for the accelerator opening angle can be changed through the selection of the drive mode according to driver preference.

      2. The drive mode can be selected by operating the drive mode select switch.

      3. The selected drive mode will be shown on the multi-information display in the combination meter assembly.

        B0082ZOC01
        *1 Electric Parking Brake Switch Assembly - -
        *a Drive Mode Select Switch *b This illustration is an example only.
        Characteristics of Drive Mode
        Drive Mode Characteristics
        NORMAL Mode This drive mode provides optimum driveability.
        ECO Mode The ECM optimizes fuel economy and driving performance by gradually generating the motive force in comparison to the accelerator pedal operation. At the same time, the ECM supports eco driving by optimizing air conditioning performance.
        SPORT Mode The ECM controls motive force in the intermediate area of the accelerator pedal opening to a greater degree than that of NORMAL mode, improving acceleration performance. In addition, engine speed response performance has been improved in the high area of the accelerator pedal opening, thus producing a sporty drive.
  4. FAIL-SAFE


    1. The fail-safe function minimizes the loss of operability when an abnormality occurs in a sensor or a shift solenoid valve.

    2. For details, refer to the Repair Manual.

  5. DIAGNOSIS


    1. When the ECM detects a malfunction, the ECM records the malfunction and memorizes the information related to the fault. Furthermore, the ECM illuminates the Malfunction Indicator Lamp (MIL) in the combination meter assembly to inform the driver.

    2. The ECM will also store Diagnostic Trouble Codes (DTCs) of the malfunctions. The DTCs stored in the ECM are output to the Global TechStream (GTS) via the DLC3.

    3. For details, refer to the Repair Manual.