6R60 - Automatic Transaxle/Transmission
Transmission Electronic Control SystemTransmission Electronic System
The transmission control module (TCM) and its input/output network control the following operations:
^ Shift timing
^ Clutch pressure (shift feel)
^ Line pressure (shift feel)
^ Torque converter clutch
In addition, the TCM receives input signals from certain transmission-related sensors. The TCM also uses these signals when determining transmission operating strategy.
Using all of these input signals, the TCM can determine when the time and conditions are right for a shift or when to apply or release the torque converter clutch. It will also determine the pressure needed to optimize shift feel. To accomplish this, the TCM uses 6 pressure control solenoids and one shift solenoid to control transmission operation.
The following provides a brief description of each of the sensors and actuators used to control transmission operation.
Transmission Control Module (TCM) and Main Control Valve Body
The TCM and main control valve body are a combination of hydraulic and electronic control units. Both of these modules are installed in the transmission inside the transmission fluid pan.
Transmission Control Module (TCM)
The TCM for the transmission is mounted on top of the main control valve body. The TCM for the transmission has been designed to operate correctly in the environment in which the TCM is located.
The TCM is activated and deactivated by the ignition supply and is connected to the transmission harness by a 16-pin connector.
The TCM controls the operation of the transmission. The TCM processes information in both analog and digital forms, such as:
^ transmission input speed.
^ transmission output speed.
^ throttle position.
^ gear selection.
^ engine torque.
^ engine speed.
^ transmission fluid temperature (TFT).
^ brake pedal position (BPP).
^ engine oil temperature.
^ engine coolant temperature.
^ ABS wheel speed.
The information is then used by the TCM to decide which shift pattern to select and for shift energy management. Electro-hydraulic solenoid valves and pressure regulators control the transmission gear changes.
Five pressure regulators and one solenoid valve are used to control direct transmission fluid flow to select internal clutches and control the fluid pressure at the clutch. A separate pressure regulator is used exclusively for torque converter clutch control.
The TCM monitors all transmission inputs and outputs to confirm correct system operation. If a fault occurs, the TCM is able to carry out default action. It informs the driver of the problem through the instrument cluster diagnostic MIL light.
The TCM will shut down if the TCM hardware temperature rises above a predetermined temperature. Prior to shutting down, the TCM will log a fault code and enter a mechanical limp-home mode.
Solenoids
The hydraulic module contains one solenoid valve. The solenoid valve is activated by the TCM and is either open or closed. It is used to switch the position valve.
There are 6 electronic pressure control valves which convert an electronic current into a proportional hydraulic pressure. They are energized by the TCM and actuate the valves belonging to the relevant switching elements.
Solenoids VFS1, VFS3 and VFS6 are proportional in operation, meaning that hydraulic pressure increases with an increase in current. Solenoids VFS2, VFS4 and VFS5 are inversely proportional in operation, meaning that hydraulic pressure decreases with an increase in current. Solenoid SS1 is a shift solenoid having a ON/OFF operation.
Controller Area Network (CAN) Interface
For the TCM to carry out shift point and shift quality management, a number of external signals are required. For shift point management alone, the TCM requires output speed sensor, throttle pedal position, brake pedal status, gear selection position, transmission fluid temperature, four wheel drive (4WD) position, traction control, engine speed and engine torque. The controller area network (CAN) bus is used to share information between control modules.
Brake Pedal Position (BPP) Switch
The brake pedal position (BPP) switch tells the TCM when the brakes are applied. The torque converter clutch disengages when the brakes are applied. The BPP switch closes when the brakes are applied and opens when they are released.
Cylinder Head Temperature (CHT) Sensor
The cylinder head temperature (CHT) sensor is a thermistor device in which resistance changes with the temperature. The electrical resistance of a thermistor decreases as temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
Accelerator Pedal Position (APP) Sensor
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal. The APP sensor detects the position of the accelerator pedal and inputs this information as a voltage to the PCM. The PCM broadcasts the APP on the CAN bus. The TCM reads APP off the CAN message. The PCM uses the APP sensor information to aid in determining shift scheduling and torque converter control.
Turbine Shaft Speed (TSS) Sensor
The turbine shaft speed (TSS) sensor is a Hall-effect type sensor.
The TSS sensor is mounted internally and is located on the transmission control module.
Output Shaft Speed (OSS) Sensor
The output shaft speed (OSS) sensor is a Hall-effect type sensor.
The OSS sensor is mounted internally and is located on the transmission control module.
Transmission Fluid Temperature (TFT) Sensor
The transmission fluid temperature (TFT) sensor is located on the TCM. The TCM uses the sensor input to activate various shift strategies. The sensor is in the form of a temperature-dependent resistor.
The resistance value of the TFT sensor varies with temperature change. The TCM monitors the voltage across the TFT to determine the temperature of the transmission fluid.
The TCM uses this initial signal to determine whether a cold start shift schedule is necessary. The TCM also inhibits torque converter clutch operation at low transmission fluid temperatures.
Transmission Range (TR) Sensor
The TCM uses the position of the transmission range (TR) sensor, housed in the TCM, to determine the selected gear range from the range selector lever.
The TR sensor completes the start circuit in P and N, and the back-up lamp circuit in R. The sensor also opens/closes a set of switches that are monitored by the TCM to determine the position of the manual lever (P, R, N, D, 3, 2 and 1).
Transmission Operational Strategies
Adaptive Shift Strategy
Adaptive shift strategy is comprised of:
^ Shift Energy Management - this function involves reducing or increasing engine output torque during shifting.
^ Reduces excessive energy of the friction packs
^ Increases transmission service life
^ Improves shift quality
^ Unique shift schedules are selected based on vehicle operation conditions and environmental conditions
^ Trailer towing mode
^ Pressure Modulation - this function monitors the hydraulic pressure in a shift. This pressure must be matched accurately to the transmission input torque to better provide shift comfort.
^ Shift Quality Adapts - is used to provide a higher quality and consistent shift feel. Monitoring and adapting shift pressures and shift energy to overcome hardware variability over time achieve this.
^ The TCM has the ability to control the engine output torque during the shift, synchronized with the operation of the transmission clutches.
^ Trailer towing mode uses a different shift and converter map. This new map reduces the number of gearshifts when towing, climbing steep hills and while driving at higher altitudes.
Transmission Control Module (TCM) Monitoring Functions
The TCM monitors all transmission input and output to identify possible transmission failures. If a fault is detected, the TCM takes the appropriate action to make sure that the transmission enters a safe mode of operation.
^ Voltage Supply - this function monitors the vehicle battery voltage.
^ Watchdog Monitoring - the watchdog monitoring has 2 functions:
^ Checks for faults in the driver circuits by activating each driver.
^ Checks to see if the safety circuit is functioning correctly.
^ TCM Temperature - If the TCM temperature rises above a predetermined temperature, the TCM will shut down. Prior to shutting down, the TCM will log a fault code during shutdown. The transmission will enter a mechanical limp-home mode.
^ Pressure Regulator/Solenoid - Each pressure regulator and solenoid is monitored for open and short circuits. The TCM also checks that the current being delivered to each solenoid valve or pressure regulator is within limits.
^ Torque Converter Control - The TCM checks and verifies that the torque converter has been engaged correctly. If the torque converter has not engaged correctly, the TCM will carry out the fail-safe action of opening the converter clutch.