Transmission Control Systems: Description and Operation

DESCRIPTION

Transaxle Electronic Control System - Component Locator:

The Powertrain Control Module (PCM) and its input/output network control the following transaxle operations:
^ shift scheduling
^ Line pressure (shift feel)
^ torque converter clutch scheduling
^ coast braking
The transaxle control is separate from the engine control strategy in the PCM, although some of the input signals are shared.
^ The powertrain control module receives and sends electrical signals that are used to make the transaxle more responsive to driver and vehicle needs.

INPUT SIGNALS
The PCM receives input signals from engine-related sensors:
^ Mass Air Flow sensor (MAF sensor).
^ Engine Coolant Temperature (ECT) sensor and the Electronic Ignition (EI) system.
These signals provide information to the powertrain control module about 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 (TP) sensor. Still other inputs are provided by the following:
^ Vehicle Speed Sensor (VSS)
^ Brake On/Off (BOO) switch
^ Turbine Shaft Speed (TSS) sensor
^ Air Conditioning Clutch (A/C)
^ Power Steering Pressure (PSP) switch
^ Transmission Range (TR) sensor (controlled by the driver placement of the transaxle range selector lever)
^ Transmission Fluid Temperature (TFT) sensor
Using all of these input signals, the powertrain control module can determine when to schedule a shift or torque converter clutch application.

OUTPUT SIGNALS
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 shift solenoids.
^ one pulse-width modulated Torque Converter Clutch (TCC) solenoid for Torque Converter Clutch (TCC) control.
^ an Electronic Pressure Control (EPC) solenoid for line pressure control.

ADDITIONAL OPERATION
The PCM also has the ability to:
^ Monitor its input and output devices for the presence of faults.
^ Store Diagnostic Trouble Codes (DTC's) related to detected faults.
^ Alert the driver for some detected faults by turning on the Malfunction Indicator Lamp (MIL) in the instrument cluster.
^ Display information when a service technician connects diagnostic equipment.
The powertrain control module receives and sends electrical signals that are used to make the transaxle more responsive to driver and vehicle needs. The driver demands are transmitted to the PCM through three components:
Transaxle Range Selector Lever:
The driver's demand for a particular gear range is translated into an electrical signal for the PCM by the TR sensor.
Accelerator Pedal
The driver's demand for torque and acceleration are sent mechanically to the throttle body sensor then translates this mechanical motion into an electrical signal that is monitored by the PCM.
Brake Pedal
A Brake On/Off (BOO) switch tells the PCM when the brake is applied, indication the driver demand to disengage the torque converter.