Part 2
System Description (Continued)D Position in 4th Gear
^ Hydraulic pressure is applied to the 4th clutch, then the 4th clutch engages the mainshaft 4th gear with the mainshaft.
^ The mainshaft 4th gear drives the countershaft 4th gear and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 4th gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.
D Position in 5th Gear
^ Hydraulic pressure is applied to the servo valve to engage the reverse selector with the countershaft 5th gear while the shift lever in the forward range (D, D3, 2, and 1 positions).
^ Hydraulic pressure is applied to the 5th clutch, then the 5th clutch engages the mainshaft, 5th gear with the mainshaft.
^ The mainshaft 5th gear drives the countershaft 5th gear, which drives the reverse selector hub and the countershaft.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
^ Hydraulic pressure is also applied to the 1st clutch, but since the rotation speed of 5th gear exceeds that of 1st gear, power from 1st gear is cut off at the one-way clutch.
R Position
^ Hydraulic pressure is applied to the servo valve to engage the reverse selector with the countershaft reverse gear while the shift lever in the R position.
^ Hydraulic pressure is applied to the 5th clutch, then the 5th clutch engages the mainshaft reverse gear with the mainshaft.
^ The mainshaft reverse gear drives the countershaft reverse gear via the reverse idler gear.
^ The countershaft reverse gear drives the countershaft via the reverse selector which drives the reverse selector hub.
^ The rotation direction of the countershaft is changed by the reverse idler gear.
^ Power is transmitted to the final drive gear, which in turn drives the final driven gear.
Electronic Control System
Function Diagram
The electronic control system consists of the powertrain control module (PCM), sensors, and seven solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.
The PCM receives input signals from the sensors, switches, and other control units, processes data, and outputs signals for the engine control system and the A/T control system. The A/T control system includes shift control, grade logic control, clutch pressure control, lock-up control, and auxiliary transmission fluid pump control. The PCM switches the shift solenoid valves and the A/T clutch pressure control solenoid valves to control shifting transmission gears and lock-up torque converter clutch.
Electronic Controls Locations:
Shift Control
The PCM instantly determines which gear should be selected by various signals sent from sensors and switches, and it actuates shift solenoid valves A, B, C, and D to control shifting transmission gear.
The shift solenoid valves have two types:
^ Shift solenoid valves A and D use ON-OPEN/OFF-CLOSE type; shift solenoid valve opens the port of shift solenoid valve pressure while shift solenoid valve is turned ON by the PCM, and closes the port when shift solenoid valve is OFF.
^ Shift solenoid valves B and C use ON-CLOSE/OFF-OPEN type; shift solenoid valve closes the port of shift solenoid valve pressure while shift solenoid valve is turned ON by the PCM, and opens the port when shift solenoid valve is OFF.
The combination of driving signals to shift solenoid valves A, B, C, and D are shown in the table.
The vehicle starts off in 1st, then 2nd in a few seconds when the shift lever is shifted into the D or D3 position from the N, shifts automatically to 3rd, 4th, and 5th, and downshifts through 4th, 3rd, and 2nd in the D position; shifts automatically to 3rd, and downshifts to 2nd in the D3 position. The vehicle usually restarts off in 2nd in the D or D3 position. The vehicle can start in 1st gear in the D or D3 position, when you accelerate the vehicle from a stop at half throttle and more, and when you accelerate the vehicle at the instant of shifting the shift lever into the D or D3 position from the N.
Shift Control - Grade Logic Control
The grade logic control system has been adopted to control shifting in the D and D3 positions. To control shifting while the vehicle is ascending or descending a slope, the PCM compares actual driving conditions with programmed driving conditions, based on the input from the accelerator position sensor, the engine coolant temperature sensor, the barometric pressure sensor, the brake pedal position switch signal, and the shift lever position signal.
Grade Logic Control: Ascending Control
When the PCM determines that the vehicle is climbing a hill in the D and D3 positions, the system extends the engagement area of 2nd gear, 3rd gear, and 4th gear to prevent the transmission from frequently shifting between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, so the vehicle can run smooth and have more power when needed.
NOTE: Shift commands stored in the PCM between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, enable the PCM to automatically select the most suitable gear according to the magnitude of a gradient.
Grade Logic Control: Descending Control
When the PCM determines that the vehicle is going down a hill in the D and D3 positions, the shift-up speed from 4th to 5th gear, 3rd to 4th gear, and from 2nd to 3rd (when the throttle is closed) becomes faster than the set speed for flat road driving to widen the 4th gear, 3rd gear, and 2nd gear driving areas. This, in combination with engine braking from the deceleration lock-up, achieves smooth driving when the vehicle is descending. There are three descending modes with different 4th gear driving areas, 3rd gear driving areas, and 2nd gear driving areas according to the magnitude of a gradient stored in the PCM. When the vehicle is in 5th or 4th gear and you are decelerating while applying the brakes on a steep hill, the transmission will downshift to a lower gear. When you accelerate, the transmission will then return to a higher gear.
Deceleration Control
When the vehicle goes around a corner and needs to decelerate first and then accelerate, the PCM sets the data for deceleration control to reduce the number of times the transmission shifts. When the vehicle is decelerating from speeds above 27 mph (43 km/h), the PCM shifts the transmission from 5th or 4th to 2nd earlier than normal to cope with upcoming acceleration.
Clutch Pressure Control
The PCM actuates A/T clutch pressure control solenoid valves A, B, and C to control the clutch pressure. When shifting between gears, the clutch pressure regulated by A/T clutch pressure control solenoid valves A, B, and C engage and disengage the clutch smoothly.
The PCM receives input signals from the various sensors and switches, processes data, and outputs current to A/T clutch pressure control solenoid valves A, B, and C.
Lock-up Control
Shift solenoid valve D controls the hydraulic pressure to switch the lock-up shift valve and lock-up ON and OFF. The PCM actuates shift solenoid valve D and A/T clutch pressure control solenoid valve C to start lock-up. A/T clutch pressure control solenoid valve C applies and regulates hydraulic pressure to the lock-up control valve to control the amount of the lock-up.
The lock-up mechanism operates in the D position (2nd, 3rd, 4th, and 5th), and in the D3 position (2nd and 3rd).
Auxiliary Transmission Fluid Pump (ATFP) Control
The auxiliary transmission fluid pump supplies hydraulic pressure to the hydraulic circuit during auto idle stop.
When the vehicle comes to a stop in auto idle stop mode, the ATF pump in the main valve body also stops, then the PCM and auxiliary transmission fluid pump (ATFP) control unit start the auxiliary transmission fluid pump to supply hydraulic pressure to the hydraulic circuit. The auxiliary transmission fluid pump continues to supply enough hydraulic pressure for the clutch to engage until the engine auto-starts. When the engine auto-starts, the ATFP control unit stops the auxiliary transmission fluid pump.
The PCM outputs the required amount of motor torque to the ATFP control unit. The ATFP control unit processes data, drives the auxiliary transmission fluid pump motor, and sands a feedback signal of motor torque to the PCM.
The auxiliary transmission fluid pump is bolted on the torque converter housing. The ATFP consists of the trochoid pump assembly and the 3-phase brushless DC motor.
PCM A/T Control System Electrical Connections:
PCM A/T Control System Inputs and Outputs (Part 1):
PCM A/T Control System Inputs and Outputs (Part 2):
PCM A/T Control System Inputs and Outputs (Part 3):
PCM A/T Control System Inputs and Outputs (Part 4):
Hydraulic Controls
The valve body includes the main valve body, the regulator valve body, the secondary valve body, and the accumulator body. The ATF pump is driven by splines on the end of the torque converter which is attached to the engine through the IMA motor rotor. Fluid flows through the regulator valve to maintain specified pressure through the main valve body to the manual valve, directing pressure to each of the clutches. Shift solenoid valves A, B, C, and D are mounted on the accumulator body. A/T clutch pressure control solenoid valves A, B, and C are mounted on the transmission housing. The auxiliary transmission fluid pump (ATFP) is mounted on the outside of the torque converter housing.
Main Valve Body
The main valve body contains the manual valve, the modulator valve, shift valve A, shift valve B, shift valve E, CPC valve A, the servo control valve, the lubrication check valve, the lubrication control valve, the torque converter check valve, the lock-up timing valve, the relief valve, the cooler check valve, the lock-up shift valve, and the ATF pump gears. The primary function of the main valve body is to switch fluid pressure on and off to control hydraulic pressure going to the hydraulic control system.
Regulator Valve Body
The regulator valve body is located on the main valve body. The regulator valve body contains the regulator valve, the lock-up control valve, the servo valve, and the 3rd accumulator.
Regulator Valve
The regulator valve maintains constant hydraulic pressure from the ATF pump to the hydraulic control system, while also furnishing fluid to the lubricating system and the torque converter. Fluid from the ATF pump flows through B and B'. Fluid entering from B flows through the valve orifice to the A cavity. This pressure of the A cavity pushes the regulator valve to the spring side, and this movement of the regulator valve uncovers the fluid port to the torque converter and the relief valve. The fluid flows out to the torque converter and the relief valve, and the regulator valve returns under spring force. According to the level of the hydraulic pressure through B, the position of the regulator valve changes, and the amount of fluid from B' through the torque converter changes. This operation is continued, maintaining the line pressure.
Increases in hydraulic pressure according to torque are performed by the regulator valve using stator torque reaction. The stator shaft is splined to the stator in the torque converter, and its arm end contacts the regulator spring cap. When the vehicle is accelerating or climbing (torque converter range), stator torque reaction acts on the stator shaft, and the stator arm pushes the regulator spring cap in the direction of the arrow in proportion to the reaction. The stator reaction spring compresses, and the regulator valve moves to increase the line pressure which is regulated by the regulator valve. The line pressure reaches its maximum when the stator torque reaction reaches its maximum.
Secondary Valve Body
The secondary valve body is on the main valve body. The secondary valve body contains shift valve C, shift valve D, CPC valve B, CPC valve C, the reverse control valve, and the reverse CPC valve.
Accumulator Body
The accumulator body is on the secondary valve body, and contains the 1st, 1st-hold, 2nd, 4th, and 5th accumulators. The 3rd accumulator is in the regulator valve body.
Hydraulic Flow
Distribution of Hydraulic Pressure
As the engine turns, the ATF pump starts to operate, and the auxiliary transmission fluid pump operates during auto idle stop. Automatic transmission fluid (ATF) is drawn through the ATF strainer (filter) and discharged into the hydraulic circuit. Then, ATF flowing from the ATF pump becomes line pressure that is regulated by the regulator valve. Torque converter pressure from the regulator valve enters the torque converter through the lock-up shift valve and lock-up control valve, and it is discharged from the torque converter. The torque converter check valve prevents torque converter pressure from rising.
The PCM controls shift solenoid valves A, B, C, and D ON and OFF, and the shift solenoid valves control shift solenoid pressure to the shift valves. Applying shift solenoid pressure to the shift valves moves the position of the shift valve, and switches the port of hydraulic pressure. The PCM also controls A/T clutch pressure control solenoid valves A, B, and C. The A/T clutch pressure control solenoid valves regulate the A/T clutch pressure control solenoid valve pressure and apply A/T clutch pressure control solenoid valve pressure to CPC valves A, B, and C.
When shifting between gears, the clutch is engaged by pressure from the CPC pressure mode. The PCM controls one of the shift solenoid valves to move the position of the shift valve. This movement switches the port of CPC pressure and line pressure. Line pressure is then applied to the clutch, and CPC pressure is released. Engaging the clutch with line pressure mode happens when shifting is completed.
N Position
Line pressure (1) regulated by the regulator valve flows to shift solenoid valves. The PCM controls the shift solenoid valves ON and OFF. The conditions of the shift solenoid valves and positions of the shift valve are as follows:
^ Shift solenoid valve A is OFF, and closes the port of shift solenoid valve A pressure (SA); shift valve A stays on the left side.
^ Shift solenoid valve B is turned ON, and closes the port of shift solenoid valve B pressure (SB); shift valve B and shift valve E stay on the left side.
^ Shift solenoid valve C is OFF, and opens the port of shift solenoid valve C pressure (SC); shift valve C and shift valve D move to the right side.
^ Shift solenoid valve D is OFF, and closes the port of shift solenoid valve D pressure (SD).
Line pressure (1) also flows to the modulator valve and becomes modulator pressure (6). Modulator pressure (6) flows to the A/T clutch pressure control solenoid valves. The manual valve covers the port leading pressure to the clutches, and the hydraulic pressure is not applied to the clutches.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
D and D3 Positions: 1st gear shifting from the N position
Shift solenoid valves remain the same as in the N position when shifting to the D position from the N position. The manual valve is moved to the D position, and uncovers the port of line pressure (4) leading to CPC valves A and C. The PCM controls A/T clutch pressure control solenoid valves A and C, the A/T clutch pressure control solenoid valve A pressure (56) flows to CPC valve A, and the A/T clutch pressure control solenoid valve C pressure (58) flows to CPC valve C. CPC valves A and C regulate line pressure (4), line pressure (4) becomes the CPC C pressure (4C) at CPC valve C, and becomes the CPC A pressure at CPC valve A. The CPC C pressure (4C) becomes the 1st clutch pressure (10) at shift valve D, and 1st clutch pressure flows to the 1st clutch. CPC A pressure (4A) becomes the 2nd clutch pressure (20) at shift valve B via shift valve A. The 1st clutch and 2nd clutch engage gently with the CPC pressure mode.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
D and D3 Positions: Driving in 1st gear
PCM turns shift solenoid valve C ON, and shift solenoid valve C covers the port of the shift solenoid valve C pressure (SC) to shift valves C and D. Shift solenoid valve A keeps OFF, and shift solenoid valve B keeps ON. Shift valves C and D are moved to the left side, shift valve D switches the port of line pressure (4) and the CPC C pressure (4C) leading to the 1st clutch, and shift valve C switches the port of the CPC A pressure (5A) releasing 2nd clutch pressure. Line pressure (4) becomes the 1st clutch pressure (10) at shift valve D, and flows to the 1st clutch. The 1st clutch is engaged securely with the line pressure mode.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
D and D3 Positions: Shifting between 1st gear and 2nd gear
As the speed of the vehicle reaches the programmed value, the PCM turns shift solenoid valve A ON, and shift solenoid valve A uncovers the port of the shift solenoid valve A pressure (SA) to shift valve A. Shift solenoid valves B and C remain ON. Shift valve A is moved to the right side to uncover the port of the CPC A pressure (4A) leading to the 2nd clutch. The PCM controls A/T clutch pressure control solenoid valve A, and A/T clutch pressure control solenoid valve A pressure (56) is applied to CPC valve A. CPC valve A regulates line pressure (4), and line pressure (4) becomes the CPC A pressure (4A). The CPC A pressure (4A) flows to shift valve B via shift valves C and A, and becomes the 2nd clutch pressure (20) at shift valve B. The 2nd clutch is engaged with the CPC pressure mode. The list clutch is also engaged, but no power is transmitted because of the one-way clutch.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
D and D3 Positions: Driving in 2nd gear
PCM turns shift solenoid valve C OFF, and shift solenoid valve C uncovers the port of the shift solenoid valve C pressure (SC) to shift valve C. Shift solenoid valves A and B remain ON. Shift valve C is moved to the right side to switch the port of line pressure (4) and the CPC A pressure (4A) leading to the 2nd clutch. The CPC A pressure (513) (5K) changes to line pressure (513) (5K) and the 2nd clutch pressure (20) is changed to line pressure mode, and the 2nd clutch is engaged with the line pressure mode. The 1st clutch is also engaged, but no power is transmitted because of the one-way clutch.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
