CVT System Description - Electronic Control System

CVT System Description - Electronic Control System

Electronic Control System

Electronic Control

The electronic control system consists of the powertrain control module (PCM), sensors, switches, and solenoid valves. Shifting is 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 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 solenoids to control pulley control valves A and B shifting transmission pulley ratios.






Pulley Pressure Control/Shift Control

To reduce belt slippage and increase belt life, the PCM calculates signals from the 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 driven 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 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.






Electronic Control System (cont'd)

Start Clutch Pressure Control

The hydraulic-controlled start clutch controls smooth starting-off and creeping in D, S, L, and R like a torque converter. The PCM inputs signals from the sensors, and switches, and actuates the start clutch pressure control valve to regulate the clutch reducing pressure, and the clutch reducing pressure controls the start clutch.






PCM CVT Control System Electrical Connections ('06 Model)





Electronic Control System (cont'd)

PCM CVT Control System Electrical Connections ('07-09 Models)





PCM CVT Control System Inputs and Outputs





NOTE: Standard battery voltage is about 12 V.

PCM CONNECTOR A (square) (44P)





Electronic Control System (cont'd)

PCM CVT Control System Inputs and Outputs (cont'd)





NOTE: Standard battery voltage is about 12 V.

PCM CONNECTOR B (triangle) (44P)





*1: '06 model

PCM CONNECTOR B (triangle) (44P)





Electronic Control System (cont'd)

PCM CVT Control System Inputs and Outputs (cont'd)





NOTE: Standard battery voltage is about 12 V.

PCM CONNECTOR C (circle) (44P)





*1: '06 model

*2: '07-09 models

Self-diagnosis

If the PCM detects the failure of a signal from a sensor, a switch, a solenoid valve, or from another control unit, it stores a Temporary DTC or a DTC. Depending on the failure, a DTC is stored in either the first or the second drive cycle. When a DTC is stored, the PCM blinks the D indicator and/or turns on the malfunction indicator lamp (MIL) by a signal sent to the gauge control module via F-CAN.

- One Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit, the PCM stores a DTC for the failure and blinks the D indicator and/or turns on the MIL immediately.

- Two Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit in the first drive cycle, the PCM stores a Temporary DTC. The D indicator and the MIL do not turns on at this time. If the failure continues in the second drive cycle, the PCM stores a DTC and blinks the D indicator and/or turns on the MIL.

Fail-safe Function

When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit, the PCM ignores that signal and substitutes a pre-programmed value for them that allow the automatic transmission to continue driving. This causes a DTC to be stored and the D indicator to blink and/or the MIL to come on.