CVT System Description Electronic Control System (CVT)
CVT System Description - Electronic Control System
Electronic Control System
Electronic Control
The electronic control system consists of the PCM, sensors, switches, and solenoid valves.
The PCM receives input signals from sensors, switches, other control units, processes data, and outputs signals for the engine control system and the CVT control system. The CVT control system includes shift control, pulley pressure control, start clutch pressure control, and reverse inhibitor control. The PCM actuates the pulley control solenoid valves to control pulley control valves A and B shifting transmission pulley ratios.
Pulley Pressure Control/Shift Control
To reduce steel belt slippage and increase steel belt life, the PCM calculates signals from sensors and switches, and actuates the pulley pressure control solenoid valves to maintain optimum pulley pressure. When the pulley ratio is low (low vehicle speed), high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage. When the pulley ratio is high (high vehicle speed), high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.
The PCM compares actual driving conditions with programmed driving conditions to control shifting, and it instantly determines a drive pulley ratio from various signals sent from sensors and switches. The PCM activates the CVT drive pulley pressure control solenoid valve to control pulley pressure to the pulleys. The drive pulley drives the driven pulley via a steel belt at varying ratios ranging from 2.526 to 0.421 in D and 4.510 to 1.725 in R.
Grade Logic Control: Ascending Control
When the PCM determines that the vehicle is climbing a hill in D, the system selects the most suitable shift schedule based on the steepness of the grade so the vehicle can run smoothly and have more power when needed.
Grade Logic Control: Descending Control
When the PCM determines that the vehicle is going down a hill in D, the system selects the most suitable shift schedule based on the steepness of the grade so the vehicle can run smoothly in combination with engine braking.
Shift-Hold Control
When driving on winding roads, and the throttle is suddenly released and the brakes are applied, as is the case when decelerating at the entrance of a curve, the Shift-Hold Control keeps the transmission in its current (lower) ratio as it negotiates the corner and accelerates out. When the vehicle is driven aggressively on a winding road, the PCM will keep the engine speed on a higher-than-normal setting, so the vehicle can run smooth and have more power. The transmission will resume the normal setting after the PCM determines that normal driving has resumed.
3-Mode Drive System
This vehicle is equipped with the 3-Mode Drive System. The transmission control system controls the drive system by switching between the Normal Mode (standard drive mode), the ECON Mode, and the Sport Mode using a gear map, imparting the characteristics of each mode to the running of the vehicle.
Normal Mode
This mode controls the drive system so that, when the accelerator pedal is depressed only slightly during acceleration, the engine revolutions are kept mainly constant with respect to the speed of the vehicle, and when the accelerator pedal is depressed by a large amount, acceleration is maintained within a practical running limit without imparting stress on the vehicle and passengers.
ECON Mode
This mode controls the drive system so that, when the accelerator pedal is depressed only slightly during acceleration, the engine revolutions are kept lower than the Normal Mode with respect to the speed of the vehicle, improving fuel economy. By lowering the response in engine revolutions with respect to the amount by which the accelerator pedal is depressed during acceleration, gear change responsiveness is softened and economy improved. However, when the accelerator pedal is depressed by a large amount, the same control is used as in the Normal Mode to maintain acceleration performance.
Sport Mode
This mode controls the drive system so that, when the accelerator pedal is depressed only slightly during acceleration, torque is improved over the Normal Mode with assistance from the IMA motor, maintaining powerful running of the engine. By increasing the response in engine revolutions with respect to the amount by which the accelerator pedal is depressed during acceleration, gear change responsiveness and torque during acceleration are improved.
Change the shift map
Reduce or increase the engine speed increasing ratio
Change the driving characteristic
Each driving mode has a specialized shift map. Using information collected from the sensors, each shift map has specific shift points designed to keep the engine in its optimum rpm range for power and economy. The target engine rpm and the vehicle speed in each mode on a smooth, level road at light, normal, and wide open throttle position is shown in the graphs below.
Normal Mode
ECON Mode
Sport Mode
Smart-Paddle Shift Mode
When in the Normal Mode or the ECON Mode, engage the smart-paddle shift mode by pressing either of the steering wheel mounted paddle shifters while driving in D. In this mode, the transmission can downshift by pressing the paddle shifter - (downshift switch), or upshift by pressing the paddle shifter + (upshift switch). Each time the transmission is shifted to any of the seven speeds using the paddles, the shift indicator in the gauge control module displays the current position. The system returns to the automatic shift mode and the shift indicator display turns off when the paddle shifter + (upshift switch) is held for about 2 seconds, when the optional Mode switch is pressed, or when the PCM detects a steady cruise.
Manual-Paddle Shift Mode
In D, the Sport Mode has two modes; the automatic shift mode and the manual-paddle shift mode. In the sport driving mode, the transmission keeps the engine at a higher rpm than the Normal Mode or the ECON Mode setting, and the steering wheel-mounted paddle shifters are ready to be activated to switch to the manual-paddle shift mode. In the sport driving mode, the shift indicator and the M indicator in the gauge control module do not come on.
When the paddle shifter + (upshift switch) or paddle shifter - (downshift switch) is pressed, the sport driving mode is canceled and the manual-paddle shift mode comes into operation. The shift indicator displays the number of the selected position, and the M indicator comes on. In the manual-paddle shift mode, the driver can shift up and down manually from 1st through 7th positions by using the paddle shifters, much like a manual transmission. The paddle shifters are installed on the back of the steering wheel, and the driver can shift positions by pressing the paddle shifters without taking either hand off the steering wheel.
In the manual-paddle shift mode, the transmission must be shifted up and down by pressing the paddle shifters. However, if the vehicle is coasting at a speed that would cause the engine to over-rev by downshifting, the transmission will not downshift when the paddle shifter - (downshift switch) is pressed. The shift indicator blinks the number of the selected position several times, then returns to the current position. If the vehicle speed reaches an appropriate speed while the shift indicator is blinking, the transmission downshifts and the shift indicator displays the selected position. Likewise, if the vehicle speed is below an appropriate speed to upshift when the paddle shifter + (upshift switch) is pressed, the transmission will not upshift. The shift indicator blinks the number of the selected position several times, and then returns to the number of the current position. If the vehicle speed reaches an appropriate upshift speed while the shift indicator is blinking, the transmission upshifts and the shift indicator displays the selected position.
This mode has automatic upshifting areas to prevent engine over-revving, and downshifting areas so the vehicle can run smoothly with more power to cope with upcoming acceleration. When coasting, the transmission downshifts to the next lower position if the vehicle slows down to the programmed speed, or by pressing the brake pedal.
When the transmission decelerates to a stop, the transmission shifts to 1st position automatically. The transmission can be shifted to 2nd position by pressing the paddle shifter + (upshift switch) while the vehicle is stopped, and the vehicle can start off in 2nd position.
The number of the selected position goes off from the shift indicator, the M indicator goes off, and the system changes from the manual-paddle shift mode when the paddle shifter + (upshift switch) is held for about 2 seconds or when the optional Mode switch is pressed.
L mode
For maximum engine braking and power for climbing, activate the L mode by pressing the paddle shifter + (upshift switch) and the paddle shifter - (downshift switch) at the same time and hold them for about 5 seconds. The shift indicator displays an L while in this mode. The system will return to the automatic shift mode and the shift indicator display turns off when the paddle shifter + (upshift switch) and the paddle shifter - (downshift switch) are held at the same time for about 2 seconds or when the optional Mode switch is pressed.
Start Clutch Pressure Control
The hydraulic-controlled start clutch, like a torque converter, controls smooth starting-off and creeping in D and R. The PCM inputs signals from the sensors and the switches, and actuates the CVT clutch pressure control solenoid valve to regulate the clutch reducing pressure, and the clutch reducing pressure controls the start clutch.
PCM CVT Control System Electrical Connections
PCM Inputs and Outputs at Connector A (square) (44P)
PCM Inputs and Outputs at Connector B (triangle) (44P)
PCM Inputs and Outputs at Connector C (circle) (44P)
