Transmission Control Systems: Description and Operation
DESCRIPTIONThe A4LD Transmission is an electronically controlled four speed automatic transmission. The Powertrain Control Module (PCM) uses inputs from various sensors to control the operation of the A4LD Transmission.
The A4LD Transmission has self-test capabilities much like those in other electronic control systems.
INPUTS & OUTPUTS
The Constant Control Relay Module (CCRM) supplies power to the PCM and PCM system related components. When the Ignition Switch is turned to "RUN" or "START", voltage is applied to the 3-4 Shift Solenoid and the Torque Converter Clutch (TCC) Solenoid.
The Throttle Position (TP) Sensor is a potentiometer. The sensor output is a DC voltage that varies with throttle angle. By monitoring the TP Sensor output and other sensors, the PCM calculates the proper transmission line pressure, shift scheduling, and Torque Converter Clutch.
The Profile Ignition Pickup (PIP) signal is produced by Electronic Ignition (EI). It sends RPM and Crankshaft position information to the PCM to determine shift scheduling and torque converter operation.
The 3-4 Shift Solenoid provides gear selection of third and fourth gears by controlling the pressure to the shift valves.
The Torque Converter Clutch (TCC) Solenoid provides the torque converter clutch control by shifting the converter clutch control valve to apply or release the torque converter clutch.
The Vehicle Speed Sensor generates an AC signal that is proportional to vehicle speed.
The PCM uses this speed signal and other inputs to determine the shift scheduling and converter clutch control.
The Brake On/Off (BOO) Switch is used to prevent converter clutch operation when the brake has been depressed. This input is ignored if the Throttle Position Sensor indicates more than one third throttle position.
The Engine Coolant Temperature Sensor is a thermistor in which resistance decreases as engine coolant temperature increases. The PCM measures the voltage drop across the Engine Coolant Temperature Sensor and uses this information to help calculate fuel delivery, spark timing and EGR control and clutch converter operation.