Transaxle Electronic Control System: Notes

Shift timing, shift feel (line pressure) and torque converter clutch (TCC) control in the automatic transaxle are controlled electronically by the PCM and its input/output network. The transaxle control is separate from the engine control strategy in the PCM, although some of the input signals are shared. Some input signals come from the engine-related sensors, mass air flow (MAF) sensor or engine coolant temperature (ECT) sensor to give the PCM an idea of the load and climate under which the engine is operating. Some other inputs are based on driver inputs, such as accelerator pedal position which is relayed to the PCM by the throttle position (TP) sensor. Still other inputs are provided by the transaxle itself, from sensors such as the transmission range (TR) sensor (controlled by the placement of the transaxle range selector) and the transmission fluid temperature (TFT) sensor. Using all of these input signals, the PCM can determine when the time and conditions are right for a shift or converter clutch application. The PCM can also determine the line pressure needed to optimize shift feel. To accomplish these functions, the PCM controls 5 electronic solenoids, 2 ON/OFF solenoids for shifting, one pulse width modulating (PWM) solenoid for torque converter clutch control, an electronic pressure control (EPC) solenoid for line pressure control and a 3-2 timing/coast clutch solenoid to control the release of the coast clutch and the coordinated release of the direct clutch and the apply of the low and intermediate band, during a 3-2 downshift.