Transaxle Electronic Control System
Transaxle Electronic Control System
Electronic System Description
The PCM and its input/output network control the following operations:
- Shift timing
- Line pressure (shift feel)
- Torque Converter Clutch (TCC)
The transaxle control is separate from the engine control strategy in the PCM, although some of the input signals are shared. When determining the best operating strategy for transaxle operation, the PCM uses input information from certain engine-related and driver-demand related sensors and switches.
In addition, the PCM receives input signals from certain transaxle-related sensors and switches. The PCM also uses these signals when determining transaxle operating strategy.
Using all of these input signals, the PCM can determine when the time and conditions are right for a shift, or when to apply or release the TCC (Torque Converter Clutch). It will also determine the best line pressure needed to optimize shift engagement feel. To accomplish this, the PCM uses output solenoids to control transaxle operation.
The following provides a brief description of each of the sensors and actuators used to control transaxle operation.
Electronic Ignition (EI)
The Electronic Ignition (EI) system consists of the PCM, a Crankshaft Position (CKP) sensor and ignition coils. The CKP (Crankshaft Position) sensor sends a crankshaft position signal to the PCM. The PCM then sends the appropriate ignition signal to the ignition coils. The PCM also uses this signal as well as Wide Open Throttle (WOT) shift control, TCC (Torque Converter Clutch) control and electronic pressure control.
Accelerator Pedal Position (APP)
The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal. The APP (Accelerator Pedal Position) detects the position of the accelerator pedal and inputs this information as a voltage to the PCM. The PCM uses APP (Accelerator Pedal Position) sensor information to aid in determining line pressure, shift scheduling and TCC (Torque Converter Clutch) operation. Failure of this sensor will cause the transmission to operate at higher line pressure to avoid damage to the transmission. This higher line pressure causes harsh upshifts and harsh engagements.
Throttle Position (TP) Sensor
The Throttle Position (TP) sensor is a potentiometer mounted on the Throttle Body (TB). The TP (Throttle Position) sensor detects the position of the throttle plate and sends this information to the processor assembly as varying voltage signal.
The PCM uses the monitored voltage level of the TP (Throttle Position) sensor for control of Line Pressure Control (LPC) , TCC (Torque Converter Clutch) operation and shift scheduling.
If a malfunction occurs in the TP (Throttle Position) sensor circuit, the processor will recognize that the TP (Throttle Position) sensor signal is out of specification. The processor will then operate the transaxle in a high capacity mode to prevent transaxle damage.
PCM
The PCM controls operation of the transaxle. Many input sensors provide information to the PCM. The PCM then controls the actuators which affect transaxle operation.
Transmission Range (TR) Sensor Assembly
The Transmission Range (TR) sensor assembly is an internally mounted sensor that includes the detent bracket and is located above the main control assembly. The components of the TR (Transmission Range) sensor are factory adjusted and is installed as a calibrated assembly. The TR (Transmission Range) sensor contains electronic circuitry that provides the PCM a fixed frequency duty cycle for each of the various positions of the manual lever (PARK, REVERSE, NEUTRAL, DRIVE and LOW to the PCM). The PCM uses the TR (Transmission Range) sensor signal for engine start, reverse lamps, LPC (Line Pressure Control) , shift scheduling and TCC (Torque Converter Clutch) operation.
Brake Pedal Position (BPP) Switch
The Brake Pedal Position (BPP) switch tells the PCM when the brakes are applied. The BPP (Brake Pedal Position) switch closes when the brakes are applied and opens when they are released. The BPP (Brake Pedal Position) signal is used for the brake shift interlock actuation.
Turbine Shaft Speed (TSS) Sensor
This Turbine Shaft Speed (TSS) sensor is a Hall-effect pickup that sends a signal to the PCM that indicates transaxle turbine shaft input speed. The TSS (Turbine Shaft Speed) sensor provides converter turbine speed information for TCC (Torque Converter Clutch) strategy. Also used in determining static LPC (Line Pressure Control) pressure settings.
Output Shaft Speed (OSS) Sensor
The Output Shaft Speed (OSS) sensor is a Hall-effect pickup, located on the transfer shaft drive gear, that sends a signal to the PCM to indicate transmission output speed. The OSS (Output Shaft Speed) is used for TCC (Torque Converter Clutch) control and shift scheduling.
Solenoid Body
NOTICE: If the solenoid body identification and strategy does not match the solenoid body information in the Powertrain Control Module (PCM), transaxle damage or driveability concerns can occur.
The solenoid body contains 7 solenoids, 5 shift solenoids (Shift Solenoid A (SSA) , Shift Solenoid B (SSB) , Shift Solenoid C (SSC) , Shift Solenoid D (SSD) and Shift Solenoid E (SSE)), TCC (Torque Converter Clutch) solenoid and LPC (Line Pressure Control) solenoid. The Transmission Fluid Temperature (TFT) is also located in the solenoid body. The solenoid body is serviced as an assembly.
The solenoid body has a unique strategy data file that must be downloaded to the PCM. There is a 7-digit solenoid body identification and a 13-digit solenoid body strategy for each solenoid body. Any time a new solenoid body is installed or a new transaxle is installed, the scan tool must be used to get the solenoid body strategy data file and download it into the PCM.
If the PCM is replaced, the solenoid body identification and solenoid body strategy must be downloaded into the PCM.
Line Pressure Control (LPC) Solenoid
The LPC (Line Pressure Control) solenoid is a Variable Force Solenoid (VFS) that varies hydraulic pressure by actuating a hydraulic valve.
The PCM applies variable current to the LPC (Line Pressure Control) solenoid which varies pressure in the VBS LINE hydraulic circuit to the main pressure regulator valve. Refer to Hydraulic Circuits Hydraulic Circuits for additional information.
The LPC (Line Pressure Control) solenoid uses inversely proportional operation. As the current from the PCM decreases, the pressure from the solenoid increases. As the current from the PCM increases, the pressure from the solenoid decreases. The LPC (Line Pressure Control) solenoid is supplied hydraulic pressure from the SOL FD circuit.
With zero current, the LPC (Line Pressure Control) solenoid fully opens the hydraulic valve which applies the maximum amount of hydraulic pressure to the Main Pressure Regulator Valve through the VBS LINE hydraulic circuit and applies maximum line pressure in the LINE hydraulic circuit. With maximum current to the solenoid, the hydraulic valve fully closes the outlet port for minimum pressure to the VBS LINE hydraulic circuit to lower the line pressure in the LINE hydraulic circuit.
Line Pressure Control (LPC) Inversely Proportional Variable Force Solenoid (VFS)
Torque Converter Clutch (TCC) Solenoid
The TCC (Torque Converter Clutch) solenoid is a VFS (Variable Force Solenoid) that varies hydraulic pressure by actuating a hydraulic valve.
The PCM applies variable current to the TCC (Torque Converter Clutch) solenoid which varies pressure in the VBS TCC hydraulic circuit to the TCC (Torque Converter Clutch) regulator valve and the TCC (Torque Converter Clutch) control valve. Refer to Hydraulic Circuits Hydraulic Circuits for additional information.
The TCC (Torque Converter Clutch) solenoid uses proportional operation. As the current from the PCM decreases, the pressure from the solenoid decreases. As the current from the PCM increases, the pressure from the solenoid increases. The TCC (Torque Converter Clutch) solenoid is supplied hydraulic pressure from the SOL FD circuit.
With zero current, the TCC (Torque Converter Clutch) solenoid fully closes the hydraulic valve which applies the minimum amount of hydraulic pressure to the TCC (Torque Converter Clutch) regulator valve through the VBS TCC hydraulic circuit and releases the TCC (Torque Converter Clutch). With maximum current to the solenoid, the hydraulic valve fully opens the outlet port for maximum pressure to the VBS TCC hydraulic circuit to apply the TCC (Torque Converter Clutch).
Torque Converter Clutch (TCC) Proportional Variable Force Solenoid (VFS)
Shift Solenoid A (SSA) , Shift Solenoid B (SSB) , Shift Solenoid C (SSC) and Shift Solenoid D (SSD)
Shift solenoids A-D are variable force type solenoids that vary hydraulic pressure by actuating a hydraulic valve.
The PCM applies variable current to the shift solenoids which varies pressure in the hydraulic circuit to the regulator and latch valves of the clutch that it controls. Refer to Hydraulic Circuits Hydraulic Circuits for additional information.
SSA (Shift Solenoid A) and SSC (Shift Solenoid C) use proportional operation. As the current from the PCM decreases, the pressure from the solenoid decreases. As the current from the PCM increases, the pressure from the solenoid increases. SSA (Shift Solenoid A) and SSC (Shift Solenoid C) are supplied hydraulic pressure from the SOL FD circuit.
With zero current, SSA (Shift Solenoid A) and SSC (Shift Solenoid C) fully close the hydraulic valves which applies zero amount of hydraulic pressure to the clutch regulator and latch valves of the clutch that it controls and releases the clutch. With maximum current to the solenoids, the hydraulic valves are fully open for maximum pressure to the clutch regulator and latch valves to apply the clutch.
Shift Solenoid A (SSA) and Shift Solenoid C (SSC) Proportional Variable Force Type Solenoids
SSB (Shift Solenoid B) and SSD (Shift Solenoid D) use inversely proportional operation. As the current from the PCM decreases, the pressure from the solenoid increases. As the current from the PCM increases, the pressure from the solenoid decreases. SSB (Shift Solenoid B) and SSD (Shift Solenoid D) are supplied hydraulic pressure from the SOL FD circuit.
With zero current, SSB (Shift Solenoid B) and SSD (Shift Solenoid D) fully open the hydraulic valves which applies maximum hydraulic pressure to the clutch regulator and latch valves to apply the clutch that it controls. With maximum current to the solenoids, the hydraulic valve is fully closed to apply zero amount of hydraulic pressure to the clutch regulator and latch valves of the clutch that it controls and releases the clutch.
Shift Solenoid B (SSB) and Shift Solenoid D (SSD) Inverse Proportional Variable Force Type Solenoids
Shift Solenoid E (SSE)
SSE (Shift Solenoid E) is an ON/OFF solenoid. When SSE (Shift Solenoid E) is in the ON position, SSD (Shift Solenoid D) controls the clutch regulator and latch valves to apply the low/reverse clutch. When SSE (Shift Solenoid E) is in the OFF position, SSD (Shift Solenoid D) controls the clutch regulator and latch valves to apply the overdrive (4, 5, 6) clutch. Refer to Hydraulic Circuits Hydraulic Circuits for additional information.
SSE (Shift Solenoid E) is supplied hydraulic pressure from the SOL FD circuit. When SSE (Shift Solenoid E) is OFF, the solenoid supply is blocked and the outlet port (ON/OFF SIG circuit) is connected to the exhaust port. When SSE (Shift Solenoid E) is ON, the exhaust port is blocked and the solenoid supply is connected to the outlet port (ON/OFF SIG circuit), supplying pressure to the clutch control bypass valve.
Shift Solenoid E (SSE) ON/OFF Solenoid
