Dodge ram truck 3500 1996 Service Manual page 1347

B R FUEL SYSTEM 14 - 1 1 3
G E N E R A L I N F O R M A T I O N (Continued)
ated or regulated by the PCM. These components are
the:
• Fuel tank
• Fuel tank module
@ Low and high-pressure fuel supply lines
• Low-pressure, mechanical, fuel transfer pump
(fuel lift pump)
• High-pressure fuel injection pump
• Fuel filter/water separator
* • Fuel heater
• Fuel heater relay
• Fuel shutdown solenoid
• Fuel shutdown solenoid relay
• High-pressure fuel injectors
• Fuel return line
• Fuel filter (strainer)
® Fuel drain manifold
D E S C R I P T I O N A N D O P E R A T I O N
SYSTEM DIAGNOSIS
The PCM can test many of its own input and out­
put circuits. I f the PCM senses a fault in a major
system, the PCM stores a Diagnostic Trouble Code
(DTC) in memory.
Technicians can display stored DTCs by two differ­
ent methods. The first is to cycle the ignition switch
On - Off - On - Off - On within 5 seconds. Then count
the number of times the malfunction indicator (check
engine) lamp on the instrument panel flashes on and
off. The number of flashes represents the DTC. There
is a slight pause between the flashes representing
the first and second digits of the code. Longer pauses
separate individual trouble codes.
The second method of reading DTCs uses the DRB
scan tool. For DTC information, refer to Group 25,
Emission Control Systems. See On-Board Diagnos­
tics.
POWERTRAIN CONTROL MODULE (PCM)—DIESEL
The powertrain control module (PCM) is located in
the right-rear side of the engine compartment (Fig.
1). I t is mounted to the dash panel cowl with three
bolts. The PCM was formerly referred to as the
SBEC or engine controller. Except for operation of
the intake manifold air heater elements, the PCM
does not regulate or control fuel system operation on
the diesel engine.
The PCM is a pre-programmed, dual micro-proces­
sor digital computer. Although i t 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
Fig. 1 PCM Location
• 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.
NOTE: PCM Inputs:
• Air conditioning selection
• Battery voltage
• 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
NOTE: PCM Outputs: