Dodge ram truck 3500 1996 Service Manual page 1276

14 - 42 FUEL SYSTEM
D E S C R I P T I O N A N D O P E R A T I O N (Continued)
THREE-FOUR SHIFT SOLENOID—PCM OUTPUT
This output is used to control the transmission
three-four shift solenoid. I t is used on 4-speed elec­
tronically controlled automatic transmissions only.
TORQUE CONVERTOR CLUTCH (TCC) SOLENOID—
PCM OUTPUT
This circuit controls operation of the transmission
mounted torque convertor clutch (TCC) solenoid used
for torque convertor engagement.
The powertrain control module (PCM) will deter­
mine when to engage and disengage the solenoid by
monitoring vehicle miles per hour (mph) versus the
output voltage of the throttle position sensor. Also
needed are various Inputs from:
• Engine coolant temperature
• Module timer
• Engine rpm
• MAP sensor
MANUAL TRANSMISSION
I f equipped with a manual transmission, this PCM
output will control operation of the shift indicator
lamp (if equipped with lamp). The lamp Is controlled
by the powertrain control module (PCM). The lamp
Illuminates on the instrument panel to indicate when
the driver should shift to the next highest gear for
best fuel economy. The PCM will turn the lamp OFF
after 3 to 5 seconds i f the shift of gears is not per­
formed. The lamp will remain off until vehicle stops
accelerating and is brought back to range of up-shift
lamp operation. This will also happen i f vehicle Is
shifted into fifth gear.
The indicator lamp is normally illuminated when
the ignition switch is turned on and i t is turned off
when the engine is started up. With the engine run­
ning, the lamp is turned ON/OFF depending upon
engine speed and load.
TRANSMISSION R E L A Y — P C I OUTPUT
The output to this relay provides battery voltage to
the overdrive (OD), torque converter clutch (TCC)
and variable force (VSS) solenoids. Once battery volt­
age Is applied to the solenoids, they are Individually
activated by the PCM through OD, TCC and VSS
outputs. The relay is located In the Power Distribu­
tion Center (PDC). Refer to label on PDC cover for
relay location.
VARIABLE FORCE SOLENOID—PCM OUTPUT
This solenoid regulates the transmission fluid line
pressure to produce the governor pressure necessary
for transmission shift control. I t is used on 4-speed
electronic transmissions only.
THROTTLE B O D Y — 3 . 9 L / 5 . 2 L / 5 . 9 L ENGINES
Filtered air from the air cleaner enters the intake
manifold through the throttle body (Fig. 30). Fuel
does not enter the intake manifold through the throt­
tle body. Fuel is sprayed into the manifold by the fuel
injectors. The throttle body is mounted on the intake
manifold. I t contains an air control passage (Fig. 31)
controlled by an idle air control (IAC) motor. The air
control passage is used to supply air for idle condi­
tions. A throttle valve (plate) is used to supply air for
above idle conditions.
THROTTLE BODY
Fig. 30 Throttle Body—3.9L/5.2L/5.9L Engines
Fig. 31 Air Control Passage—3.9U5.2U5.9L Engines
The throttle position sensor (TPS), idle air control
(IAC) motor and manifold absolute pressure sensor
(MAP) are attached to the throttle body. The acceler-