Dodge ram truck 3500 1996 Service Manual page 1355

B R FUEL SYSTEM 14 - 121
DESCRIPTION AND OPERATION ( C o n t i n u e d )
SPEED CONTROL SOLENOIDS—PCM OUTPUT
Speed control operation is regulated by the power-
train control module (PCM). The PCM controls the
vacuum to the throttle actuator through the speed
control vacuum and vent solenoids. Refer to Group
8H for Speed Control Information.
TACHOMETER—PCM OUTPUT
The powertrain control module (PCM) supplies
engine rpm values to the instrument cluster tachom­
eter. Refer to Group 8E for tachometer information.
TORQUE CONVERTOR CLUTCH (TCC) SOLENOID—
PCM OUTPUT
AUTOMATIC TRANSMISSION ONLY
TORQUE CONVERTER CLUTCH
AND OVERDRIVE SOLENOID
ELECTRICAL CONNECTOR
VEHICLE
SPEED
SENSOR J9414-59
Fig. 16 Eiectrical Connections at Transmission—
TCC and Overdrive Solenoids
The powertrain control module (PCM) will deter­
mine when to engage and disengage the solenoid by
monitoring vehicle miles per hour (mph). Also needed
are various inputs from the module timer, engine
rpm and throttle position sensor.
TRANSMISSION TEMPERATURE WARNING •
LAMP—PCM OUTPUT
AUTOMATIC TRANSMISSION ONLY
An instrument panel mounted lamp (Fig. 17) is
used to warn of a possible transmission fluid over­
heating condition. When transmission fluid tempera­
ture has been determined to be above approximately
280 degrees F by the transmission temperature sen­
sor, a signal is sent to the powertrain control module
(PCM). The PCM will then control warning lamp
operation. The lamp will illuminate for about two
seconds each time the ignition key is initially turned
to the ON position as a bulb check.
This feature is used with certain heavy-duty auto­
matic transmissions only.
Also refer to Transmission Temperature Sensor—
PCM Input for additional information.
INSTRUMENT
Fig. 17 Transmission Temperature Warning
Lamp—Typical Location
WAIT-TO-START LAMP WARNING LAMP—PCM
OUTPUT
The wait-to-start warning lamp is turned on and
off by the PCM based on the intake manifold air tem­
perature sensor input. The lamp is located on the
instrument panel.
The lamp is turned on when the ignition is first
activated. I f the PCM reads intake manifold air tem­
perature below 15°C (59°F), i t will turn the wait-to-
start warning lamp on for the air heater preheat
cycle. The lamp stays on until the preheat cycle is
over.
The wait-to-start lamp will flash on and off i f the
intake manifold air temperature sensor input to the
PCM is below minimum value or above maximum
value. The PCM stores a DTC when these conditions
occur.
Refer to Intake Manifold Air Heater for additional
information.
D I A G N O S I S A N D T E S T I N G
VISUAL INSPECTION .
:
A visual inspection for loose, disconnected, or incor­
rectly routed wires and hoses should be made before
attempting to diagnose or service the diesel fuel
injection system. A visual check will help find these
conditions. I t also saves unnecessary test and diag­
nostic time. A thorough visual inspection of the fuel
injection system includes the following checks:
(1) Be sure that the battery connections (on both
batteries) are tight and not corroded.