General Description

PCM Wiring:

SYSTEM DESCRIPTION
The 4T80-E transaxle is electronically controlled by the Powertrain Control Module (PCM). Inputs to the PCM determine the shift pattern and [1][2]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 (TPC) 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

Torque Converter Clutch (TCC) Solenoid - The TCC solenoid is applied with a pulse width modulated duty cycle to control the rate of TCC apply.

Transaxle Pressure Control (TPC) 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 (TPS) - 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 (TIS) 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.

TRANSAXLE ADAPT FUNCTION
The 4T80-E uses a line pressure control system which has the ability to continuously adapt the system's line pressure (increase as needed) to compensate for normal wear of clutch fiber plates, seals, springs, etc. This "learning" feature is similar to what is used for fuel control (integrator / block learn) and throttle position (idle learn). The PCM maintains several adapt parameters for the transaxle:

Upshift Adapt - The PCM monitors the TIS Sensor and VSS during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the TPC solenoid signal to maintain a set shift feel.

Steady State Adapt - The PCM monitors the TIS Sensor and VSS after a shift and calculates the amount of slippage in that gear. The PCM then adjusts the TPC solenoid signal to maintain slippage below a set amount.

Garage Shift Adapt - The PCM monitors TIS Sensor during a shift into a given range (P, R, N, D) and calculates if the engagement is occurring too fast (harsh) or too slow. The PCM adjusts the TPC solenoid to maintain a set (desirable) shift feel.