Control Module: Description and Operation
DESCRIPTIONNOTE: The Transmission Control Module (TCM) is integrated with the Powertrain Control Module (PCM).
Several sensors and switches allow the 4EAT system to constantly monitor driving conditions. Signals from these sensors and switches representing vehicle speed and engine load are sent to the PCM where the information is utilized to control the transaxle shift pattern, gear position, and torque converter lockup timing.
The PCM has built-in self diagnosis, fail safe, and diagnostic trouble code display functions for the main input sensors and solenoid valves.
Self Diagnosis Function
The Powertrain Control Module has internal self diagnosis functions to warn the driver if a malfunction occurs in any of the main input sensors or output solenoids. If a malfunction occurs, the Malfunction Indicator Lamp (MIL) (CHECK ENGINE lamp) flashes.
Fail Safe Function
When the self diagnosis function detects a malfunction, the Powertrain Control Module will maintain minimum driveability through the fail safe system by substituting the signal from a component that is operating correctly for the signal from the failed component. The fail safe function will then continue a normal lockup and shift pattern to maintain minimum driveability.