Dodge RAM TRUCK 1500 1995 Service Manual page 1125

I R
COMPONENT DESCRIPTION/SYSTEM OPERATION—EXCEPT DIESEL 14-43
in the engine compartment (Fig. 25). For the location
of the relay within the PDC, refer to PDC cover.
Fig. 25 Power Distribution Center (PDC) Location
EGR VALVE CONTROL SOLENOID—PIN #35—PCM
OUTPUT
This circuit controls operation of the exhaust gas
recirculation (EGR) valve solenoid.
Refer to Group 25, Emission Control System for in­
formation.
T R A N S M I S S I O N T E M P E R A T U R E W A R N I N G
LAMP—PCM PIN #36—PCM OUTPUT
8.0L ENGINE—AUTOMATIC TRANSMISSIONS
ONLY
An instrument panel mounted lamp (Fig. 23) is
used to warn of a possible transmission overheating
condition. When transmission temperature has been
determined to be above approximately 280 degrees F
by the transmission temperature sensor, a signal is
sent to the powertrain control module (PCM). The
PCM will then control lamp operation. The lamp will
illuminate for about two seconds each time the igni­
tion key is initially turned to the ON position as a
bulb check.
On 3.9L/5.2L/5.9L engines, pin #31 performs the
same function.
Also refer to Transmission Temperature Sensor—
PCM Pin #42-PCM Input for additional informa­
tion.
OVERDRIVE LAMP—PCM PIN #37—PCM OUTPUT
3.9L/5.2L/5.9L
ENGINES—AUTOMATIC
TRANSMISSIONS ONLY
This circuit controls a signal for the operation of
the instrument panel mounted overdrive lamp. On
the 8.0L V-10 engine, this circuit is controlled by pin
#31. When the lamp is illuminated, the overdrive is
engaged.
8.0L V-10 ENGINE
Pin #37 is used to supply a dwell gate signal for
operation of the ignition control module. The dwell
gate signal selects which coil is to be fired.
FUEL INJECTORS—PCM PIN #38—PCM OUTPUT
3
m
9L/5«2U5»9L
ENGINES
Pin #38 is used as the ground control circuit for the
fuel injector on cylinder #5 on 3.9L/5.2L/5.9L engines.
Refer to Fuel Injectors-PCM Pin #13-PCM Output
for information.
8.0L V-10 ENGINE
Pin #38 is used to supply a dwell signal for opera­
tion of the ignition control module to energize the ig­
nition coil.
IDLE AIR CONTROL (IAC) MOTOR—PIN #39—PCM
OUTPUT
Pin #39 controls one of the circuits for operation of
the IAC motor.
The IAC motor is mounted to the throttle body
(Figs. 26 or 27) and is controlled by the powertrain
control module (PCM).
Fig. 26 IAC Motor—3.9U5.2U5.9L Engines—Typical
The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage (Figs. 28 or 29) and regulates air
flow through it. Based on various sensor inputs, the
powertrain control module (PCM) adjusts engine idle
speed by moving the IAC motor pintle in and out of
the air control passage. The IAC motor is positioned
when the ignition key is turned to the ON position.