Dodge ram truck 3500 1996 Service Manual page 636

8W - 30 - 2 8W - 30 FUEL/IGNITION SYSTEMS B R
D E S C R I P T I O N AMD O P E R A T I O N (Continued)
K118 connects to cavity C15 of the PCM. Circuit K4
connects to cavity A4.
DATA LINK CONNECTOR
Circuit M l supplies battery voltage to the data
link connector. Circuit M l originates at cavity 7 of
Joint Connector B.
Circuit D20 connects to cavity C29 of the Power-
train Control Module (PCM). Circuit D20 is the SCI
receive circuit for the PCM.
Circuit D21 connects to. cavity C27 of the 'PCM.
Circuit D21 is the SCI transmit circuit for the PCM.
Circuits Z l l and Z12 provide ground for' the data
link connector.
AUTOMATIC SHUT DOWN (ASD) RELAY
When the ignition switch is in the START or RUN
position, it connects circuit A l from fuse 8 in the
Power Distribution Center (PDC) to circuit A21. Cir­
cuit A21 powers circuit F18 through fuse 9 in the
fuse block. Circuit F18 supplies battery voltage to the
coil side of the ASD relay. The Powertrain Control
Module (PCM) provides the ground path for the coil
side of the relay on circuit K51. Circuit K51 connects
to cavity C3 of the PCM.
When the PCM grounds the ASD relay, the relay
contacts close and connect circuit A16 from fuse 4 in
the PDC to circuit A142. Circuit A142 splices to sup­
ply voltage to the fuel injectors, ignition coil, and
heated oxygen sensors. Circuit A142 also connects to
cavity C12 of the PCM.
FUEL PUMP RELAY
Circuit A14 from fuse 8 in the Power Distribution
Center (PDC) supplies battery voltage to the contact
side of the fuel pump relay. Circuit A21 from the
ignition switch powers circuit F18 through 9 in the
fuse block. Circuit F18 supplies battery voltage to the
coil side of the Automatic Shut Down (ASD) and fuel
pump relays. The Powertrain Control Module (PCM)
provides the ground path for the coil side of the fuel
pump relay on circuit K31. Circuit K31 connects to
cavity C19 of the PCM connector.
When the PCM grounds the fuel pump relay, the
contacts CLOSE and connect circuits A14 and A61.
Circuit A61 supplies voltage to the fuel pump motor
(part of the in-tank fuel pump module).
HELPFUL INFORMATION " •' ' '
Circuit A14 also connects to cavity A22 of the PCM.
FUEL PUMP MODULE .
The in-tank fuel pump module contains the fuel
pump motor and the fuel level sensor. For fuel pump
module information, refer to Group 14, Fuel System.
FUEL PUMP MOTOR
When the fuel pump relay contacts close, circuit
A61 feeds the fuel pump motor. Circuit Z13 provides
ground for the fuel pump motor.
FUEL LEVEL SENSOR
The fuel level sensor is a variable resistor. Circuit
G4 connects the fuel level sensor to the fuel gauge in
the instrument cluster. Circuit F14 from fuse 12 in
the fuse block supplies voltage to the fuel gauge. The
fuel level sensor draws voltage from circuit F14
through the fuel gauge on circuit G4. Circuit Z l l pro­
vides the ground path for the fuel level sensor.
As current flows through the coils in the fuel
gauge, it creates a magnetic field. One of the coils in
the gauge receives fixed current. The other coil is
connected to the level sensor. The magnetic field con­
trols the position of the fuel gauge pointer.
The fuel level, sensor contains a variable resistor.
As the position of the float arm on the fuel level sen­
sor changes, the resistor changes the current flow
through the second coil in the fuel gauge. A change in
current flow alters the magnetic field in the fuel
gauge, which changes the pointer position.
Circuit K104 from the level sensor connects to cir­
cuit K226. Circuit K226 connects to cavity C26 of the
Powertrain Control Module (PCM). Circuit K226 pro­
vides the fuel level input to the PCM. Circuit K4 pro­
vides ground for the level sensor signal.
FUEL PUMP MODULE—DIESEL ENGINE
The in-tank fuel pump' module used with diesel
engines contains the fuel level sensor. The diesel
engine does not use an in-tank electrical fuel pump.
For fuel pump module information, refer to Group
14, Fuel System.
FUEL LEVEL SENSOR
The fuel level sensor is a variable resistor. Circuit
G4 connects the fuel level sensor to the fuel gauge in
the instrument cluster. Circuit F14 from fuse 12 in
the fuse block supplies voltage to the fuel gauge. The
fuel level sensor draws voltage from circuit F14
through the fuel gauge on circuit G4. Circuit Z l l pro­
vides the ground path for the fuel level sensor.
As current flows through the coils in the fuel
gauge, it creates a magnetic field. One of the coils in
the gauge receives fixed current. The other coil is
connected to the level sensor. The magnetic field con­
trols the position of the fuel gauge pointer.
The fuel level sensor contains a variable resistor.
As the position of the float arm on the fuel level sen­
sor changes, the resistor changes the current flow
through the second coil in the fuel gauge. A change in
current flow alters the magnetic field in the fuel
gauge, which changes the pointer position.