Transaxle Control and Diagnostics

The automatic transaxle as well as the engine is controlled by a powertrain control module (PCM). Part of the PCM is dedicated to the operation of the automatic transaxle referred to as the transaxle controller (TC).

The PCM/TC uses various input and output parameters to control the transaxle shifts. The PCM/TC has the ability to adjust (adapt) the shifting pressures due to build variations, normal transaxle wear, and environmental conditions.

Along with controlling the transaxle, the PCM/TC also incorporates extensive built-in diagnostics which constantly monitors the transaxle operation. When certain fault conditions are detected the PCM will store a diagnostic trouble code and illuminate the MIL telltale lamp to notify the driver that a fault condition has occurred. Some detected faults will not turn on an indicator lamp, but will store an information flag in the PCM to aid in diagnosing a problem. The diagnostic trouble codes and information flags which get stored into the PCM/TC are designed to determine when mechanical faults as well as electrical faults have occurred.

The transmission diagnostic charts were developed to diagnose many of the possible problems associated with the automatic transaxle. These charts will lead to the repair of wiring, sensors, transaxle internal components, or the PCM.

For complete PCM testing information and procedures, refer to Computers and Control Systems. Computers and Control Systems