System

Electronic Transmission Control System:

Purpose:
The electronic transmission control system utilizes a controller that monitors a number of engine and vehicle functions, then uses this data to control the following operations:
- [1][2]Torque converter clutch engagement
- Upshift pattern
- Downshift pattern
- Line pressure to control shift quality

The controller used on diesel engine applications is referred to as a Transmission Control Module (TCM). The TCM controls transmission functions only.

On gasoline engine applications, the TCM and ECM are combined into one unit known as a Powertrain Control Module (PCM). The PCM controls a number of engine functions such as fuel control, EGR and ignition timing, in addition to the transmission functions.


Operation:
The PCM/TCM uses the following information sensors to gather data for electronically controlling transmission functions.
- Transmission temperature sensor
- Coolant Temperature Sensor (CTS)
- Engine speed sensor (diesel only)
- Transmission input speed sensor
- Transmission output speed sensor
- Pressure switch manifold
- Brake switch

The PCM/TCM constantly looks at information from the various sensors, and controls the systems that affect transmission and vehicle performance. By recognizing operational problems the PCM/TCM is able to perform a diagnostic function and flash codes which identify problem areas, thus aiding the technician in making repairs.

The PCM/TCM 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.

Location:
The PCM/TCM is located in the passenger compartment and is the control center of the electronic transmission control system.