RAM 1500 Van V6-3.9L VIN X (1997)
Hydraulic Control Unit: Description and Operation
Hydraulic Valve
Front Wheel
Hydraulic Control Unit
GENERAL INFORMATION
The Hydraulic Control Unit (HCU) assembly consist of the front antilock valve assembly and a pump/motor unit. The assembly is mounted to a
one piece bracket and a stud plate on the driver side inner fender panel just below the battery tray. A molded, flexible plastic shield is used to
protect the top of the valve assembly.
FRONT ANTILOCK VALVE
The front brake antilock valve consists of a solenoid valve body. The antilock valve provides two channel pressure control of the front brakes. One
channel controls the left front brake unit. The second channel controls the right front brake unit. Each front brake unit is controlled independently.
The solenoid valves are cycled open and closed as needed during antilock braking. They are cycled rapidly and continuously to modulate brake
fluid pressure and control wheel lock-up and deceleration.
PUMP/MOTOR
The pump is run by a DC type motor, controlled by the Controller Antilock Brake (CAB). The pump supplies the additional fluid volume needed
during antilock braking.
CIRCUIT OPERATION
Circuit B120 from the Anti-Lock Brake System (ABS) power relay supplies voltage for the pump motor plus the isolation and dump solenoids in
the front hydraulic valve. The Controller, Anti-Lock Brakes (CAB), activates the pump motor and solenoids by providing separate ground paths
for each.
The CAB provides a ground path for the motor on circuit B60.
The CAB controls the isolation and dump solenoids in the front hydraulic valve by providing a ground path for each on separate circuits:
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Circuit B248 connects to cavity 30 of the CAB and provides ground for the right front dump solenoid.
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Circuit B249 connects to cavity 33 of the CAB and provides ground for the right front isolation solenoid.
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Circuit B243 connects to cavity 35 of the CAB and provides ground for the left front dump solenoid.
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Circuit B245 connects to cavity 37 of the CAB and provides ground for the left front isolation solenoid.
There are two reset switches in the front hydraulic valve; a left switch and a right switch. Both switches provide inputs to the CAB. Circuit B5
from the left reset switch connects to the CAB at cavity 5 while circuit B18 from the right reset switch connects to cavity 18.
