Electronic System Description - Ford 1999 Taurus V8-3.4L VIN N SHO Service Manual

Electronic System Description

Need a step-by-step guide?

Get an AI-powered repair guide with parts lists, cost estimates, and clear instructions for your 1999 Ford.

Shift timing, shift feel (line pressure) and torque converter clutch control in the AX4S are controlled electronically by the Powertrain Control Module (PCM) and its input/output network. The transmission control is separate from the engine control strategy in the powertrain control module, although some of the input signals are shared.

Some input signals come from the engine-related sensors, for example, mass air flow sensor (MAP sensor) and Engine Coolant Temperature sensor (ECT sensor) to give the powertrain control module 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 related to the powertrain control module by the Throttle Position sensor (TP sensor). Still other inputs are provided by the transaxle itself, from sensors such as the Vehicle Speed Sensor (VSS), Transmission Range (TR) sensor (controlled by the placement of the selector lever) and the transmission fluid temperature sensor.

Using all of these input signals, the powertrain control module can determine when the time and conditions are right for a shift or torque converter clutch application. The powertrain control module can also determine the line pressure needed to optimize shift feel. To accomplish these functions, the powertrain control module controls five electronic solenoids-three on/off solenoids for shifting, one pulse-width modulate solenoid for torque converter clutch control and an Electronic Pressure Control (EPC) solenoid for line pressure control.