Dodge RAM TRUCK 1500 1995 Service Manual page 1170

14 - S I COMPONENT DESCRIPTION/SYSTEM OPERATION—DIESEL ENGINE
B R
POWERTRAIN CONTROL
MODULE (PCM) J9414-11
Fig. 1 PCM Location—Typical
The PCM is a pre-programmed, dual micro-proces­
sor digital computer. Although it does not regulate or
control the fuel system on the diesel powered engine,
it does operate or regulate the:
© Speed control system
® Charging system
© Certain warning lamps
• Transmission overdrive solenoid
• Torque convertor engagement
© ASD relay
• Air conditioning operation
• Tachometer
© Intake manifold air heater
The PCM can adapt its programming to meet
changing operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo­
nents are referred to as PCM Outputs. The sensors
and switches that provide inputs to the PCM are con­
sidered PCM inputs.
PCM Inputs:
• Air conditioning selection
• Battery voltage
9 Brake light switch
© Engine speed sensor (rpm)
• Speed control switch position
© Auto shutdown (ASD) sense
• Battery voltage input used to measure generator
output
• Intake manifold air temperature sensor
• Overdrive/override switch
© Park/neutral switch (auto, trans, only)
© Power ground
© SCI receive (DRB scan tool connection)
• Sensor return
• Throttle position sensor (auto, trans, only)
• Transmission temperature sensor (auto, trans,
only)
® Vehicle speed sensor
• Water-in-fuel sensor
• Ignition switch sense
PCM Outputs:
After inputs are received by the PCM, certain sen­
sors, switches and components are controlled or reg­
ulated by the PCM. These are considered PCM
Outputs. These outputs are for:
© A/C clutch relay (A/C clutch operation)
O Auto shutdown (ASD) relay
• Data link connectors (for DRB and MDS test
equipment)
• Generator field (charging system operation)
• Malfunction indicator lamp (check engine lamp)
• Overdrive solenoid electrical operation (auto,
trans, only)
• Overdrive/Override warning lamp (auto, trans,
only)
• SCI transmit (DRB scan tool connection)
• Speed control vacuum solenoid
• Speed control vent solenoid
• Tachometer
• Torque convertor electrical operation (auto, trans,
only)
• Transmission oil temperature warning lamp (auto,
trans, only)
» Wait-to-start lamp
• Water-in-fuel lamp
• Intake Manifold Air Heater Element #1
• Intake Manifold Air Heater Element #2
PCM SYSTEM SCHEMATICS—DIESEL
A powertrain control system schematic for diesel
powered vehicles is shown in figure 2.
The schematic is displayed as a quick reference
only. It is not intended to be all-inclusive. Refer to
the Wiring Diagrams section for detailed information.
After the schematic, a description is given for each
circuit (pin/cavity) of the PCM 60-way connector.