Dodge RAM TRUCK 1500 1995 Service Manual page 628

BR
SW-32 REAR WHEEL ANTI-LOCI BRAKES 8W - 32 - 3
ALL WHEEL
A N T I - L O C K
BRAKE SYSTEM (ABS
i i i E X
page
A B S Data Link Connector
4
A B S Pump Relay . . . . . . . . . . . . . . . . . . . . . 3
A B S Warning Lamp 4
Brake Warning Lamp Switch input . . . . . . . . . . . . . .
4
Diagram Index 4
Four-Wheel Drive/PTO Switch Sense . . . . . . . . . . . 4
GENERAL INFORMATION ' .
Three fuses supply power for the Anti-Lock Brake
System (ABS); fuses 2 and 5 in the Power Distribu­
tion Center (PDC) and fuse 14 in the fuse block.
Fuses 2 and 5 in the PDC are connected directly to
battery voltage and are HOT all times. Fuse 14 is
HOT when the ignition switch is the RUN position.
In the RUN position, the ignition switch connects
circuit A2 from a 40 amp fuse in cavity 2 of the PDC
with circuit A22. Circuit A22 connects to a bus bar in
the fuse block. The bus bar feeds circuit A20 through
fuse 14. Fuse 14 is a 20 amp fuse.
Circuit' A20 is spliced and provides an ignition in­
put to the control module (cavities 12, and 17), feed
for the coil side of the ABS pump relay, feed for the
coil side of the ABS warning lamp relay, and on die­
sel engines, feed for the vacuum sensor.
Circuit Z7 provides ground for the ABS control
module. Circuit Z7 connects to cavity 20 of the ABS
control module connector. Circuit Z8 connects to cav­
ity 1 of the two-way connector.
WHEEL SPEED SENSORS
The all wheel Anti-Lock Brake. System (ABS) uses
three wheel speed sensors; a single sensor for both
rear wheels and individual sensors for the front
wheels. The single sensor used for the rear wheels
mounts on the top of the rear axle differential hous­
ing. Each sensor converts wheel speed into an elec­
trical signal that it transmits to the ABS control
module. A pair of twisted wires connect to each sen­
sor and provide signals to the ABS control module.
Circuits B6 and B7 provide signals to ABS control
module from right front wheel speed sensor. Circuit
B6 which provides the LOW signal, connects to cav­
ity 15 of the ABS control module. Circuit B7 connects
to cavity 2 of the module and provides the HIGH sig­
nal.
Circuits B8 and B9 provide signals to ABS control
module from left front wheel speed sensor. Circuit B8
which provides the LOW signal, connects to cavity 16
of the ABS control module. Circuit B9 connects to
cavity 3 of the module and provides the HIGH signal.
page
Front Anti-Lock Valve . 3
General Information 3
Rear Anti-Lock Valve 4
Stop Lamp Switch Sense
4
Vacuum Switch
4
Wheel Speed Sensors 3
Circuit B114 connects to cavity 14 of the ABS con­
trol module and to the rear wheel speed sensor. Cir­
cuit B113 connects to cavity 1 of the ABS control
module and to the rear wheel speed sensor. Circuit
B114 provides the rear wheel speed sensor HIGH in­
put while circuit B113 provides the LOW input.
'ABS PUMP RELAY
When the ABS control module grounds the ABS
pump relay on circuit B116, the relay contacts close
connecting circuit A10 from the Power Distribution
Center (PDC) and circuit B120. Circuit A10 connects
to fuse 5 in the PDC. Circuit A20 from the fuse 14 in
the fuse block splices to feed the coil side of the ABS
warning low lamp relay.
From the ABS pump relay, circuit B120 splices to
supply voltage to the ABS pump motor and all sole­
noids in the front brake anti-lock valve. Circuit B120
also supplies power to the solenoids in the rear anti-
lock valve. Additionally, circuit B120 provides an in­
put to cavity 34 of the ABS module. The input tells
the module that voltage has been supplied to the
pump motor.
FRONT ANTI-LOCI WALfE
Circuit B120 from the- ABS pump relay supplies
voltage for the ABS pump motor plus the isolation
and dump solenoids in the front anti-lock valve. The
ABS control module activates the pump motor and
the solenoids by providing separate ground paths for
each.
The ABS module provides a ground path for the
motor on circuit B60. Circuit B60 connects to cavity 2
of the ABS control module two-way connector.
The ABS control module cycles the isolation and
dump solenoids in the front anti-lock valve by provid­
ing a ground path for each on separate circuits:
• Circuit B248 connects to cavity 30 of the ABS con­
trol module and provides ground for the right front
dump solenoid.
• Circuit B249 connects to cavity 33 of the ABS con­
trol module and provides ground for the right front
isolation solenoid.