Description & Operation: Notes

The first step in diagnosing any driveability problem is verifying customer's complaint with a test drive under conditions when problem is occurring. Before entering self-diagnostics, perform a careful and complete visual inspection. Most transaxle control problems result from mechanical breakdowns or poor electrical connections. See TROUBLE SHOOTING in FORD 4F20E OVERHAUL article. Self-diagnostic system can be accessed using a New Generation Star (NGS) tester or an OBD-II compliant scan tool.

Input signals from sensors and Powertrain Control Module (PCM) are sent to Transmission Control Module (TCM). TCM can determine when time and conditions are right for a shift or converter clutch application. TCM can also determine line pressure needed to optimize shift feel. Torque Converter Clutch (TCC) solenoid minimizes lockup shock and enables powertrain to deliver a 1:1 ratio to maximize fuel economy.

Five electronic solenoids accomplish the following functions:

• 2 on/off solenoids for shifting.
• One Pulse-Width Modulator (PWM) solenoid for Torque Converter Clutch (TCC) control.
• One Electronic Pressure Control (EPC) solenoid for line pressure control.
• One coasting clutch solenoid to control release of coast clutch, coordinated release of direct clutch, and apply of the low and intermediate band.

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