Body - Dodge RAM 1500 1998 Owner's Manual

8E - 20 ELECTRONIC CONTROL MODULES
TRANSMISSION CONTROL
MODULE
DESCRIPTION
The Transmission Control Module (TCM) (Fig. 9)
may be sub-module within the Powertrain Control
Module (PCM), Engine Control Module (ECM - Diesel
only) (Fig. 10), or a standalone module, depending on
the vehicle engine. The PCM, and TCM when
equipped, is located at the right rear of the engine
compartment, near the right inner fender.
Fig. 9 PCM/TCM Location
1 - RIGHT FENDER
2 - TRANSMISSION CONTROL MODULE
3 - POWERTRAIN CONTROL MODULE
OPERATION
The Transmission Control Module (TCM) controls
all electronic operations of the transmission. The
TCM receives information regarding vehicle opera-
tion from both direct and indirect inputs, and selects
the operational mode of the transmission. Direct
inputs are hardwired to, and used specifically by the
TCM. Indirect inputs are shared with the TCM via
the vehicle communication bus.
Some examples of direct inputs to the TCM are:
• Battery (B+) voltage
• Ignition "ON" voltage
• Transmission Control Relay (Switched B+)
• Throttle Position Sensor
• Crankshaft Position Sensor
• Transmission Range Sensor
• Pressure Switches
• Transmission Temperature Sensor
• Input Shaft Speed Sensor
• Output Shaft Speed Sensor
• Line Pressure Sensor
Some examples of indirect inputs to the TCM
are:
Fig. 10 Diesel ECM
1 - ENGINE CONTROL MODULE (ECM)
2 - ECM MOUNTING BOLT
3 - 50-WAY CONNECTOR
4 - SUPPORT PLATE
5 - 60-WAY CONNECTOR
• Engine/Body Identification
• Manifold Pressure
• Target Idle
• Torque Reduction Confirmation
• Engine Coolant Temperature
• Ambient/Battery Temperature
• DRBIII Scan Tool Communication
Based on the information received from these var-
ious inputs, the TCM determines the appropriate
shift schedule and shift points, depending on the
present operating conditions and driver demand.
This is possible through the control of various direct
and indirect outputs.
Some examples of TCM direct outputs are:
• Transmission Control Relay
• Solenoids
• Torque Reduction Request
Some examples of TCM indirect outputs are:
• Transmission Temperature (to PCM)
• PRNDL Position (to BCM)
In addition to monitoring inputs and controlling
outputs, the TCM has other important responsibili-
ties and functions:
• Storing and maintaining Clutch Volume Indexes
(CVI)
• Storing and selecting appropriate Shift Sched-
ules
• System self-diagnostics
DR