Dodge ram truck 3500 1996 Service Manual page 642

8W - 3 0 - 8 8W - 30 FUEL/IGNITION SYSTEMS
BR
DESCRIPTION AND OPERATION
( C o n t i n u e d )
shut down relay. Circuit Z12 provides ground for the
coil side of the relay.
Circuit A18 from the Power Distribution Center
(PDC) supplies battery voltage to the contact side of
the fuel shut down relay. When voltage is present on
circuit T40, the relay energizes and its contacts close
to connect circuits A18 and A123. Circuit A123 sup­
plies power to one of the two coils in the fuel shut
down solenoid.
When circuit A123 energizes, the fuel shut down
solenoid raises the injection pump shut down lever to
the RUN position.
When the ignition switch is released to the RUN
position, i t connects circuit A l from fuse 3 in the
PDC to circuit A21. Circuit A21 powers circuit F18
through fuse 9 in the fuse block. Circuit F18 supplies
battery voltage to the second coil in the fuel shut
down lever. When Circuit F18 energizes, the fuel
shut down solenoid holds the injection pump shut
down lever in the RUN position.
Circuit Z12 provides ground for the fuel shut down
solenoid. Refer to Group 14, Fuel Systems, for fuel
shut down solenoid operation.
INTAKE MANIFOLD AIR HEATER RELAYS—DIESEL
ENGINE
When the ignition switch is in the START or RUN
position, i t connects circuit A l from fuse 3 in the
PDC to circuit A21. Circuit A21 powers circuit F18
through fuse 9 in the fuse block. Circuit F18 supplies
battery voltage to the coil side of each intake mani­
fold air heater relay.
The Powertrain Control Module (PCM) provides
ground for the coil in each relay on separate circuits.
The PCM grounds first relay on circuit S21; i t
grounds the second relay on circuit S22.
When the first intake manifold air heater relay
energizes, its contacts close and connect circuit A19
from the left battery positive terminal to circuit A58.
Circuit A58 connects to the intake air heater.
When the second intake manifold air heater relay
energizes,' its contacts close and connect circuit A8
from the left battery positive terminal to circuit
A122. Circuit A122 connects to the intake air heater.
The intake manifold air heaters are case grounded.
Refer to Group 14, Fuel Systems, for intake manifold
heater Pre-Heat and Post-Heat Cycles.
EGR SOLENOID—DIESEL ENGINE
When the Automatic Shut Down (ASD) relay ener­
gizes, i t connects circuit A16 from fuse 4 in the
Power Distribution Center (PDC) to circuit A142. Cir­
cuit A142 powers the EGR solenoid. The EGR control
module provides' ground for the solenoid on circuit
K35.
EGR INTAKE AIR TEMPERATURE S E N S O R -
DIESEL ENGINE
The EGR intake air temperature sensor provides
an input to the EGR Control Module (PCM) on cir­
cuit K321. Circuit K321 connects to cavity 4 of the
EGR control module.
From circuit K321, the intake air temperature sen­
sor draws voltage from the EGR control module. The
sensor is a variable resistor. As intake air tempera­
ture changes, the resistance i n the sensor changes,
causing a change in current draw.
The PCM provides a ground for the intake air tem­
perature sensor signal through circuit K204. Circuit
K204 connects to cavity 5 of the EGR control module.
EGR ENGINE COOLANT TEMPERATURE S E N S O R -
DIESEL ENGINE
The EGR engine coolant temperature sensor pro­
vides an input to the EGR control module on circuit
K2.
From circuit K2, the sensor draws voltage from the
EGR control module. The sensor is a variable resis­
tor. As coolant temperature changes, the resistance
in the sensor changes, causing a change in current
draw.
The EGR control module provides ground for the
sensor signal (circuit K2) on circuit K304.
S C H E M A T I C S A N D D I A G R A M S
WIRING DIAGRAM INDEX
This section of the wiring diagrams has separate
indexes for gasoline engines and diesel engines. I f
the component you are looking for is not found here,
refer to section 8W-02 for a complete list of all com­
ponents shown in the wiring diagrams.