Automatic Transmission/Transaxle: Description and Operation

PCM Wiring:

SYSTEM DESCRIPTION:
The HYDRAMATIC 4T80-E transmission is electronically controlled by the Powertrain Control Module (PCM). Inputs to the PCM determine the shift pattern and Torque Converter Clutch (TCC) operation.

Shift points are controlled by the PCM with two shift solenoids. Oil pressure is regulated by the PCM through a transaxle pressure control solenoid (force motor). Shift schedule and TCC apply rates are also controlled by the PCM and are influenced by many sensors.

PCM CONTROLLED COMPONENTS OR SENSORS

TCC solenoid - The TCC solenoid is applied with a pulse width modulated duty cycle to control the rate of TCC apply.

Transaxle pressure control solenoid - Controls transission pressure based on PCM control. Eliminates the need for TV cable or vacuum modulator.

Shift solenoids "A" & "B" - PCM controls the application of the solenoid to control transmission shift points. Eliminates the need for TV cable and governor pressure control.

Transaxle pressure switch - Contains five normally open switches that are used to indicate transmission manual valve range to the PCM.

Transaxle Vehicle Speed Sensor (VSS) - The VSS inputs to the PCM for various uses including transmission control. VSS signal is used by the PCM for TCC, line pressure, shift timing, and torque management control.

Transaxle input speed sensor - The PCM uses input speed for control of line pressure and speed calculation. The PCM also looks at the difference between this and the VSS signal for indication of a transmission slip condition.

Transaxle temperature sensor - The sensor is used to control TCC and line pressure.