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.
Functional Diagram
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 switches the pulley control solenoids to control pulley control valves A and B shifting position and speed stage.
Electronic Control System (cont'd)
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 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.
Start Clutch Pressure Control
The hydraulic-controlled start clutch, like a torque converter controls smooth starting-off and creeping in D, S, L, and R. The PCM inputs signals from sensors, and 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.
Electronic Control System (cont'd)
PCM CVT Control System Electrical Connections ('06 Model)
PCM CVT Control System Electrical Connections ('07-11 Models)
Electronic Control System (cont'd)
PCM CVT Control System Inputs and Outputs at PCM Connector A(square)(44P)
PCM CVT Control System Inputs and Outputs at PCM Connector B(triangle)(44P)
Electronic Control System (cont'd)
PCM CVT Control System Inputs and Outputs at PCM Connector B(triangle)(44P) (cont'd)
PCM CVT Control System Inputs and Outputs at PCM Connector C (circle)(44P)
Electronic Control System (cont'd)
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 Pending or Confirmed DTC. Depending on the failure, a DTC is stored in either the first or the second drive cycle. When a Confirmed 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 Pending or Confirmed 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 Pending 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 Confirmed 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 that signal to allow the automatic transmission to continue operating. This causes a DTC to be stored and the D indicator to blink and/or the MIL to come on. The transmission may not shift normally during fail-safe operation. Do not run the test-driving diagnosis when the MIL is ON, or when the D indicator is blinks.