Powertrain Control Module

ECM:

PURPOSE
The Powertrain Control Module (PCM) is located in the passenger compartment and is the control center of the electronic transmission control system.
The PCM is designed to process the various inputs and then respond by sending the appropriate electrical signals to control transmission upshift, downshift, shift feel and [1][2]torque converter clutch engagement.


OPERATION
The PCM constantly interprets information from the various sensors, and controls the systems that affect transmission and vehicle performance. By analyzing operational problems, the PCM is able to perform a diagnostic function by displaying DTC(s) and aid the technician in making repairs.
The PCM uses the following information sensors to gather data for electronically controlling transmission functions:

^ Transmission fluid temperature sensor.
^ Engine Coolant Temperature (ECT) sensor.
^ Engine speed sensor (diesel).
^ Throttle Position (TP) sensor.
^ Transmission or transfer case vehicle speed sensor.
^ Fluid pressure switch assembly.
^ Brake switch.

CONSTRUCTION
The control module has two parts for service:
^ Controller which is the control module without the PROM (MEM-CAL).
^ PROM (Programmable Read Only Memory) which is a separate memory calibrator unit

Learning Ability
The control module has a "learning" ability which allows it to make corrections for minor variations in the fuel system to improve driveability. If the battery is disconnected, to clear diagnostic trouble codes or for other repairs. the "learning" process resets and begins again. A change may be noted in the vehicle's performance. To "teach" the vehicle, ensure the engine is at operating temperature. The vehicle should be driven at part throttle, with moderate acceleration and idle conditions until normal performance returns.


NOTE The control module must be maintained at a temperature below 85°C (185°F) at all times. This is most essential if the vehicle is put through a baking process. The control module will become inoperative if it's temperature exceeds 85°C (185°F). It is recommended that temporary insulation be placed around the control module during the time the vehicle is in a paint oven or other high temperature processes.