OPERATION
OPERATION - POWER STEERING GEAR
Turning of the steering wheel is converted into lat-
eral (side-to side) travel through the meshing of the
helical pinion teeth with the rack teeth located in the
steering gear. This lateral travel pushes and pulls
the tie rods to change the direction of the vehicle’s
front wheels.
Power assist is provided by a pump and is con-
trolled by an open-center, rotary type control valve. It
directs fluid to either side of the gear’s integral steer-
ing rack piston. Depending on the rotation of the
steering wheel, more fluid pressure is directed to one
side of the rack piston compared to the other.
Road feel is controlled by the diameter of a torsion
bar which initially steers the vehicle. As steering
effort increases, as in a turn, the torsion bar twists
causing relative rotary motion between the rotary
valve body and valve spool. This movement restricts
fluid flow to one side of the integral rack piston and
redirects fluid behind the other side of the integral
rack piston, building up hydraulic pressure, thus
assisting in the turning effort.
OPERATION - SPEED PROPORTIONAL
STEERING GEAR
The
speed-proportional
power
steering
system
reduces the steering effort required by the driver for
low speed driving and parking maneuvers. Also, at
higher speeds, more steering effort is required pro-
viding a more firm, responsive feel to the steering
system and driver.
With the engine running and the vehicle speed
between 0 km/h (0 mph) and approximately 32 km/h (20
mph), minimum steering effort is required. Between
approximately 32 km/h (20 mph) and 100 km/h (60
mph), power steering effort will gradually increase
based upon vehicle speed. Above approximately 100
km/h (60 mph), maximum steering effort is provided by
the speed proportional steering system.
Variable-effort power steering is provided by con-
trolling power steering fluid pressure at the power
steering gear. A solenoid control valve located on the
steering gear (Fig. 2) is used to control power steer-
ing gear return fluid pressure. The pressure is con-
trolled by varying the size of an orifice.
The variable-assist speed-proportional solenoid con-
trol valve is controlled by the Body Control Module
(BCM). The BCM receives the vehicle speed signal
sent from the Powertrain Control Module (PCM).
Upon receiving the vehicle speed signal from the
PCM, the BCM converts that speed signal into an
electrical current usable by the solenoid control valve
for controlling the variable effort of the power steer-
ing system.
REMOVAL - POWER STEERING GEAR
(1) Remove the battery ground cable from the
ground stud on the shock tower and isolate the
ground cable by installing the cable isolator on the
ground stud (Fig. 3).
(2) Position the front tires of the vehicle so that
they are facing Straight-Ahead.
(3) Using a steering wheel holding clamp (Fig. 4),
lock the steering wheel from rotating.
Fig. 3 Correctly Isolated Remote Ground Cable
1 - CABLE ISOLATOR
2 - GROUND STUD
3 - GROUND CABLE
Fig. 4 Steering Wheel Lock Installed (Typical)
1 - STEERING WHEEL
2 - STEERING WHEEL CLAMP
LH
GEAR
19 - 37
GEAR (Continued)