Description & Operation: Introduction

WARNING: This page is about a different car, the 2002 Ford Escape, 2001 Mazda Tribute, and 2001 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The CD4E automatic transaxle is a four-speed, front wheel drive automatic unit with electronic controls for Electronic Pressure Control (EPC), shift scheduling, 3-2 shift timing, coast braking and Torque Converter Clutch (TCC) control. The transaxle features a four-element torque converter with a torque converter clutch. The hydraulic control system of the CD4E automatic transaxle has five solenoids that control shift feel (through line pressure control), shift scheduling (through shift valve position control), modulated application of the torque converter clutch, timing of 3-2 shifts and engine braking during coast operation.

Shift timing, shift feel (line pressure) and Torque Converter Clutch (TCC) control in the CD4E are controlled electronically by the Powertrain Control Module (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, and Engine Coolant Temperature (ECT) sensor. These inputs allow the PCM to determine the load and climate in which the engine is operating. 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 five electronic solenoids:

2 On/Off solenoids for shifting.
One Pulse Width Modulating (PWM) solenoid for torque converter clutch control.
Electronic Pressure Control (EPC) solenoid for line pressure control.
3-2 timing/coast clutch solenoid to control the release of the coast clutch.
Coordinated release of the direct clutch and the apply of low and intermediate band during a 3 - 2 downshift.

The PCM has built-in self-diagnosis, fail-safe code and warning code display for the main input sensors and solenoid valves.