CVT System Description - Electronic Control System (CVT)
CVT Control System Component Location
For locations of each component on vehicle, refer to Component Location Index.
| Location Index | Component | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| CVT System Component Location Index | Speed Sensor, Transmission Fluid Temperature Sensor, TCM, Transmission Range Switch, CVT Driven Pulley Pressure Sensor, Auxiliary transmission fluid pump | ||||||||
| Shift Position Indicator Component Location Index | Paddle Shifter, Sport Mode Switch, Shift Position Indicator | ||||||||
| Conventional Brake Component Location Index | Brake Pedal Position | ||||||||
| Fuel and Emissions Systems Component Location Index | PCM, Engine RPM, Accelerator Pedal Position Sensor, Engine Coolant Temperature Sensor, Throttle Position Sensor, Manifold Absolute Pressure Sensor | ||||||||
| VSA System Component Location Index | VSA Modulator-Control Unit | ||||||||
| Gauges Component Location Index | ECON Switch | ||||||||
Electronic Control System
Functional Diagram
The electronic control system consists of the TCM, sensors, switches, and solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The TCM receives input signals from the sensors and the other control units, processes data, and outputs signals for the engine control system and the CVT control system. The CVT control system includes the shift control, the pulley pressure control, the clutch pressure control, the lock-up control, the transmission fluid pump pressure control, and the indicator control. The TCM switches the shift solenoid valves and the CVT pulley control solenoid valves to control shifting position and lock-up torque converter clutch.
Shift Control/Pulley Pressure Control
To reduce the steel belt slippage and increase the steel belt life, the TCM/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 high (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 lower hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage. When the pulley ratio is low (high vehicle speed), high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the driven pulley, and lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.The TCM/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 TCM/PCM activates the CVT drive pulley pressure control solenoid valve and the CVT driven pulley pressure control solenoid valve to control pulley pressure to the pulleys.The shift control includes the grade logic control and the shift-hold control.
Shift Control - Grade Logic Control
The grade logic control system has been adopted to control shifting in D position/mode and S position/mode. The TCM/PCM compares actual driving conditions with memorized driving conditions, based on the input signal from the various sensors and switches, to control shifting while the vehicle is ascending or descending a slope.
Grade Logic Control: Ascending Control
When the TCM determines that the vehicle is climbing a hill in D position/mode or S position/mode, the system selects the most suitable shift schedule according to the magnitude of a gradient, so the vehicle can run smooth and have more power when needed.
Grade Logic Control: Descending Control
When the TCM determines that the vehicle is going down a hill in D position/mode or S position/mode, the system selects the most suitable shift schedule according to the magnitude of a gradient, so the vehicle can run smooth in combination with engine braking.
Shift-Hold Control
When negotiating winding roads, the throttle is suddenly released and the brakes are applied, as is the case when decelerating at the entrance of a corner, 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 TCM 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 TCM determines that normal driving has resumed.
Shift Control - D-Paddle Shift Mode (Four-Position Transmission)
When the transmission is switched into the D-paddle shift mode by pulling steering wheel-mounted paddle shifters while driving in the D position/mode with general driving, the transmission can shift into a lower speed stage by pulling the paddle shifter - (downshift switch), and it can shift into a higher speed stage by pulling the paddle shifter + (upshift switch). When the transmission shifts into a lower or a higher speed stage by pulling the paddle shifters, the shift indicator in the gauge control module displays the number of currently-selected stage. This number of the speed stage goes off when the transmission downshifts automatically, or when the transmission upshifts automatically while coasting.
Shift Control - S-paddle shift mode (Four-Position Transmission)
With the SPORT mode switch turned ON in D position/mode, the transmission is switched into the sport driving mode. This mode has two shifting modes; the sport driving mode with non-stage speeds and the S-paddle shift mode. In the sport driving mode, the transmission automatically adjusts to keep the engine at a higher rpm than the general driving mode setting, and steering wheel-mounted paddle shifters are ready to be activated to switch to the S-paddle shift mode. In non-stage speeds 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 pulled, non-stage speeds sport driving mode is canceled and the S-paddle shift mode comes into operation. The shift indicator displays the number of the selected speed stage, and the M indicator comes on. In the S-paddle shift mode, the driver can shift up and down manually from 1st through 7th speed stage by using the paddle shifters, much like a manual transmission. The paddle shifters are located on the back of the steering wheel, and the driver can shift speed stages by pulling the paddle shifters without taking either hand off the steering wheel.In the S-paddle shift mode, the transmission must be shifted up and down by pulling the paddle shifters. However, the transmission cannot downshift and stays in the current stage if the paddle shifter - (downshift switch) is pulled while the vehicle is coasting at a speed that would cause the engine to over-rev by downshifting the transmission, and the shift indicator blinks the number of the selected stage several times, then returns to the number of the current stage. If the vehicle speed reaches an appropriate speed while the shift indicator is blinking the number of the selected stage, the transmission downshifts and the shift indicator displays the selected stage. The transmission also cannot upshift and stays in the current stage if the paddle shifter + (upshift switch) is pulled while driving below an appropriate upshifting speed, the shift indicator blinks the number of the selected stage several times, then returns to the number of the current stage. If the vehicle speed reaches the an appropriate upshift speed while the shift indicator is blinking the number of the selected stage, the transmission upshifts and the shift indicator displays the selected stage.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 stage 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 stage automatically. The transmission can be shifted to 2nd stage by pulling the paddle shifter + (upshift switch) while the vehicle is stopped, and the vehicle can start off in 2nd stage.The S-paddle shift mode is canceled when moving the shift lever to any position/mode other than D, or when turing the SPORT mode switch OFF.
Clutch Pressure Control
The TCM actuates the CVT clutch pressure control solenoid valve to control the forward clutch pressure and the reverse brake pressure. When the transmission is in-gear, the forward clutch pressure and the reverse brake pressure regulated by the CVT clutch pressure control solenoid valve engage and disengage the forward clutch and the reverse brake smoothly.The TCM receives input signals from the various sensors and switches, processes data, and outputs current to the CVT clutch pressure control solenoid valve.
Lock-Up Control
Shift solenoid valve B controls hydraulic pressure to lock-up ON and OFF. The TCM actuates shift solenoid valve B and the CVT lock-up clutch control solenoid valve to start lock-up. The CVT lock-up clutch control solenoid valve applies and regulates hydraulic pressure to control the volume of the lock-up. The lock-up mechanism operates in D position/mode, S position/mode, at transmission fluid temperature exceeding 68 deg.F (20 deg.C).
Auxiliary Transmission Fluid Pump Control (With Auto Idle Stop System)
The auxiliary transmission fluid pump supplies hydraulic pressure to the hydraulic circuit during the operation of the auto idle stop system.When the vehicle comes to an engine stop in the operation of the auto idle stop system, the transmission fluid pump also stops, then the TCM starts 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 restarts. When the engine restarts, the TCM stops the auxiliary transmission fluid pump.The auxiliary transmission fluid pump is installed out of the transmission housing, and consists of the relief valve, the pump, the motor, and the driver.