CVT System Description - Electronic Controls (CVT)

CVT System Description - Electronic Controls

General Operation

The continuously variable transmission (CVT) is an electrically controlled automatic transmission with drive and driven pulleys, and steel belt. The CVT provides non-stage speeds forward and 1 reverse. The entire unit is positioned in line with the engine.

Transmission

Around the out side of the flywheel is a ring gear which meshes with the starter pinion when the engine is being started. The transmission has four parallel shafts: the input shaft, the drive pulley shaft, the driven pulley shaft, and the final drive shaft. The input shaft is in line with the engine crankshaft. The drive pulley shaft and driven pulley shaft consist of movable and fixed face pulleys. Both pulleys are linked by the steel belt.
The input shaft includes the sun gear and planetary gears with carrier. The drive pulley shaft includes the drive pulley and forward clutch. The driven pulley shaft includes the driven pulley, start clutch, and the secondary driven gear which is integral with the park gear. The final drive shaft is positioned between the secondary drive gear and the final driven gear. The final drive shaft includes the final drive gear and the secondary driven gear which serves to change the rotation direction, because the drive pulley shaft and driven pulley shaft rotate the same direction. When certain conditions of the planetary gears in the transmission are engaged by the forward clutch and the reverse brake, power is transmitted from the drive pulley shaft to the driven pulley shaft to provide [L], [S], [D], and [R] positions.

Electronic Control

The electronic control system consists of the powertrain control module (PCM), sensors, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions. The PCM is located below the dashboard, behind the glove box.

Hydraulic Control

The valve bodies include the main valve body, the ATF pump body, the control valve body, the ATF pass body, and the manual valve body. The ATF pump body is bolted on the main valve body. The main valve body is bolted on the flywheel housing. The control valve body is positioned outside of the transmission housing. The ATF pass body is positioned on the main valve body, and connected hydraulic circuit between the control valve body, main valve body and internal hydraulic circuit. The manual valve body is positioned on the intermediate housing.
The ATF pump is the trochoid type, and the inner rotor is splined with the input shaft. The pulleys and clutches receive fluid from their respective feed pipes, and the reverse brake receives fluid from internal hydraulic circuit.

Shift Control

The PCM controls to shift pulley ratio the solenoids, which receiving input signal from the various sensors and switches located throughout the vehicle. The PCM actuates the CVT drive pulley pressure control valve and CVT driven pulley pressure control valve to change pulley control pressure. The drive pulley control pressure is applied to the drive pulley, and the driven pulley control pressure is applied to the driven pulley, and pulley ratio is changed to their effective ratio.

Gear Selection

The shift lever has six positions: [P] PARK, [R] REVERSE, [N] NEUTRAL, [D] DRIVE, [S] SECOND, and [L] LOW.

Position	Description
[P] PARK	Front wheels locked; park pawl engaged with park gear on the driven pulley shaft. The start clutch and forward clutch released.
[R] REVERSE	Reverse; reverse brake engaged.
[N] NEUTRAL	Neutral; the start clutch and forward clutch released.
[D] DRIVE	General driving; the transmission automatically adjusts to keep the engine at the best speed for driving under all conditions.
[S] SECOND	For rapid acceleration; the transmission selects a wider range of ratios to give better acceleration.
[L] LOW	For engine braking and power for climbing; the transmission shifts into the lowest range of the ratios.

Starting is possible only in [P] and [N] positions because of a slide-type neutral-safety switch.

7Speed Mode

This CVT is provided with the 7Speed Mode in the [D] and [S] positions. The 7Speed Mode has two modes; the 7-speed automatic mode and 7-speed manual shifting mode. In the 7-speed automatic mode, the transmission can be shifted up and down automatically in 7-stage speeds of pulley ratios, and the steering shift switch is ready to be activated. When this switch is activated, the 7-speed automatic mode will be cancelled and 7-speed manual shifting mode comes into operation. In the 7-speed manual shifting mode, the driver can shift up and down manually in 7-stage speeds with using the steering shift switches; much like a manual transmission.

Automatic Transaxle (A/T) Gear Position Indicator

The A/T gear position indicator in the instrument panel shows what position has been selected without looking down at the console. In the 7Speed Mode, the shift indicator next to the A/T gear position indicator will display speed-stage selected. The [M] indicator in the gauge assembly under the shift indicator comes ON while selecting the 7-speed manual shifting mode.

Electronic Control System

Functional Diagram

The electronic control system consists of the powertrain control module (PCM), sensors, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions.

The PCM inputs signals from the sensors, switches, and other control units, perform processing data, and outputs signals for engine control system and CVT control system. The CVT control system includes shift control/pulley pressure control, 7Speed Mode control, start clutch pressure control, reverse inhibitor control, and also a grade logic control is stored in the PCM. The PCM actuates the solenoid valves to control shifting transmission pulley ratios.

 

Electronic Controls Location

NOTE: The illustration shows the RHD model; LHD symmetrical.

 

NOTE: The illustration shows the RHD model; LHD similar.

 

Electronic Control System (cont'd)

Shift Control/Pulley Pressure Control

The PCM compares actual driving conditions with memorized driving conditions to control shifting, and instantly determines a ratio of drive pulley and driven pulley by various signals sent from sensors and switches. The drive pulley drives the driven pulley by the steel belt at a ratio between 2.367-0.407 in non-stage in the [D] and [S] positions. In the [R] position, the ratio is set to 1.326 when pressing the accelerator, and to 2.367 when the accelerator released. When the pulley ratio is low (vehicle speed is low), the driven pulley receives high pulley pressure to hold large diameter, and the drive pulley receives low pressure to hold diameter of proportion to the driven pulley. When the pulley ratio is high (vehicle speed is high), the driven pulley receives low pressure, and drive pulley receives high. The PCM actuates the pulley pressure control valves to regulate optimum pulley pressure to the pulleys for reducing belt slippage and long belt life.

 

7Speed Mode Control

This CVT is provided with the 7Speed Mode in the [D] and [S] positions. The 7Speed Mode has two modes; the 7-speed automatic mode and 7-speed manual shifting mode. The transmission switches to the 7-speed automatic mode with push of the main switch (7SPEED MODE). In the 7-speed automatic mode, the transmission can be shifted up and down automatically in 7-stage speeds of pulley ratios, and the steering shift switch is ready to be activated. When this switch is activated, the 7-speed automatic mode will be cancelled and 7-speed manual shifting mode comes into operation. In the 7-speed manual shifting mode, the driver can shift up and down manually in 7-stage speeds with using the steering shift switches; much like a manual transmission.
The 7Speed Mode is cancelled by pressing the main switch (7SPEED MODE) or when moving the shift lever to other position.

The main switch (7SPEED MODE) (A) and the steering shift switches (B) are installed on the steering wheel. The driver can select the modes and speed stages with pressing the switches without taking either hand off the steering wheel.

 

The shift indicator (A) and [M] indicator (B) are in the gauge assembly (C) next to the A/T gear position indicator (D).

 

In the 7-speed automatic mode, the shift indicator displays the number of currently-selected speed stage. The [M] indicator does not come on in this mode.
In the 7-speed manual shifting mode, the [M] indicator comes on, and the shift indicator displays the number of the selected speed stage.

Electronic Control System (cont'd)

7Speed Mode Control (cont'd)

7-speed Automatic Mode

When the transmission is switched to the 7-speed automatic mode by pressing the main switch (7SPEED MODE) while driving in the [D] or [S] position, the transmission sets the optimum speed stage automatically according to conditions such as the balance between the throttle opening and vehicle speed. The transmission shifts to the over-drive range under certain conditions coasting in 7th speed.
When switched to the 7-speed automatic mode at a vehicle stop in the [D] or [S] position, the transmission shifts into 1st speed stage, and the vehicle starts off in 1st speed. The shift indicator displays the number of the speed stage.

 

7-speed Manual Shifting Mode

The transmission is switched to the 7-speed manual shifting mode by pushing the steering shift switches from the 7-speed automatic mode, and the [M] indicator comes ON. With pushing the plus (+) switch, the transmission upshifts to the next higher speed stage, and with pusing the minus (-) switch, the transmission downshifts. The shift indicator displays the number of the selected speed stage.
When the vehicle is coasting in such a speed that the engine will over-rev by downshifting the transmission, the transmission cannot downshift until the vehicle reaches the downshift allowable speed. This mode also has automatic upshifting area to prevent engine over-revving, and downshifting area so the vehicle can run smooth and more power to cope with upcoming acceleration. The transmission shifts to the over-drive range under certain conditions coasting in 7th speed.
When the vehicle decelerates to a stop, the transmission shifts to 2nd speed stage automatically, not to 1st speed.The transmission can be shifted to 2nd speed stage by pushing the plus (+) switch while the vehicle is stopped, and the vehicle can start off in 2nd speed.

 

Start Clutch Pressure Control

Hydraulic-controlled start clutch works smooth starting-off and creeping in [D], [S], [L], and [R] positions like the torque converter. The PCM inputs signals from the sensors and switches, and actuates the start clutch pressure control valve to regulate the start clutch pressure.

 

Electronic Control System (cont'd)

PCM Terminal Connections

 

PCM Inputs and Outputs

 

PCM CONNECTOR A (31P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
A2	YEL/BLK	IGP2	Power supply circuit from main relay	With ignition switch ON (II): Battery voltage With ignition switch OFF: 0 V
A3	YEL/BLK	IGP1	Power supply circuit from main relay	With ignition switch ON (II): Battery voltage With ignition switch OFF: 0 V
A4	BLK	PG2	Ground
A5	BLK	PG1	Ground
A10	GRN/BLK	SG2	Sensor ground
A11	GRN/WHT	SG1	Sensor ground
A18	BLU/WHT	VABS	Vehicle speed sensor signal input	With ignition switch ON (II): About 5 V With ignition switch OFF: 0 V
A20	YEL/BLU	VCC2	Power supply circuit for sensors	With ignition switch ON (II): About 5 V With ignition switch OFF: 0 V
A21	YEL/RED	VCC1	Power supply circuit for sensors	With ignition switch ON (II): About 5 V With ignition switch OFF: 0 V
A23	BRN/BLK	LG2	Ground
A24	BRN/BLK	LG1	Ground

PCM CONNECTOR B (24P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
B7	GRN/WHT	DN LS +	CVT driven pulley pressure control valve power supply positive electrode	With ignition switch ON (II): Pulsing signal
B11	RED/WHT	M IND	[M] indicator control	When 7-speed manual shifting mode is selected: About 6 V In other than manual shifting mode: 0 V
B12	LT GRN	S IND	[S] indicator control	In the [S] position: About 6 V In other than the [S] position: 0 V
B16	YEL	SC LS +	CVT start clutch pressure control valve power supply positive electrode	With ignition switch ON (II): Pulsing signal

Electronic Control System (cont'd)

PCM Inputs and Outputs (cont'd)

 

PCM CONNECTOR B (24P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
B19	LT GRN/RED	S-DN	Downshift switch signal input	With ignition switch ON (II): Downshift switch pressed: 0 V Downshift switch released: About 5 V
B20	YEL	S-UP	Upshift switch signal input	With ignition switch ON (II): Upshift switch pressed: 0 V Upshift switch released: About 5 V
B24	BLU/WHT	DR LS+	CVT drive pulley pressure control valve power supply positive electrode	With ignition switch ON (II): Pulsing signal

PCM CONNECTOR C (22P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
C1	PNK/BLK	DN LS -	CVT driven pulley pressure control valve power supply negative electrode	With ignition switch ON (II): Pulsing signal
C6	GRN/BLK	SOL INH	Inhibitor solenoid control	With inhibitor solenoid ON (II): Battery voltage With inhibitor solenoid OFF: 0 V
C7	RED/BLU	NDR	CVT drive pulley speed sensor signal input	With ignition switch ON (II): 0 V or about 5 V With engine at idle in the [N] position: About 2.5 V
C8	PNK/BLU	SC LS -	CVT start clutch pressure control valve power supply negative electrode	With ignition switch ON (II): Pulsing signal
C9	BLU/WHT	ATP S	Transmission range switch [S] position input	In the [S] position: 0 V In other than the [S] position: About 5 V
C10	WHT	ATP R	Transmission range switch [R] position input	In the [R] position: 0 V In other than the [R] position: About 10 V
C11	BLU	ATP L	Transmission range switch [L] position input	In the [L] position: 0 V In other than the [L] position: About 10 V
C12	LT GRN	ATP NP	Transmission range switch [P] and [N] positions input	In the [P] and [N] positions: 0 V In other than the [P] and [N] positions: About 5 V

PCM CONNECTOR C (22P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
C13	YEL	M-SW	Main switch (7Speed Mode) signal input	In the 7Speed Mode: 0 V Released the 7Speed Mode: About 5 V
C15	WHT	NDN	CVT driven pulley speed sensor signal input	With ignition switch ON (II): 0 V or about 5 V With engine at idle in the [N] position: About 2.5 V
C16	GRN/YEL	DR LS -	CVT drive pulley control valve power supply negative electrode	With ignition switch ON (II): Pulsing signal
C20	PNK	ATP D	Transmission range switch [D] position input	In the [D] position: 0 V In other than the [D] position: About 5 V
C22	WHT/RED	VEL1	CVT speed sensor signal input	With ignition switch ON (II): 0 V or about 5 V With driving (front wheels rotating): About 2.5 V

PCM CONNECTOR E (31P)

Terminal Number	Wire Color	Signal	Description	Measuring Conditions/Terminal Voltage
E8	BLU/WHT	LED A	Shift indicator control	With ignition switch ON (II) and not in the 7Speed Mode: About 5 V In the 7Speed Mode 4th, 5th, 6th speed: About 5 V 1st, 2nd, 3rd, 7th speed: About 0.3 V
E11	PNK	D IND	[D] indicator control	When ignition switch is first turned ON (II): About 6 V for 2 seconds In the [D] position: About 6 V
E20	GRN/BLK	LED C	Shift indicator control	With ignition switch ON (II) and not in the 7Speed Mode: About 5 V In the 7Speed Mode 1st, 3rd, 5th speed: About 5 V 2nd, 4th, 6th, 7th speed: About 0.3 V
E21	RED/WHT	LED B	Shift indicator control	With ignition switch ON (II) and not in the 7Speed Mode: About 5 V In the 7Speed Mode 2nd, 3rd, 6th speed: About 5 V 1st, 4th, 5th, 7th speed: About 0.3 V
E22	WHT/BLK	BK SW	Brake pedal position switch signal input	Brake pedal pressed: Battery voltage Brake pedal released: 0 V
E29	BRN	SCS	SCS terminal signal input	With ignition switch ON (II) SCS terminals open: About 5 V SCS terminals short-circuited to ground: 0 V

Circuit Diagram