1995 ACURA TL power steering

Construction and Function

TCS Control unit

Driving Control

When the drive wheel speed exceeds the vehicle speed by a given amount, the TCS control unit judges that the drive

wheels are slipping, and it outputs the traction control signal to reduce engine power.

Handling Control

Based on signals about right and left driven wheel rotational speeds, the control unit calculates the vehicle's "yaw" rate

(the turn rate of the vehicle's body). Based on signals from the steering angle sensor, the control unit also calculates the

yaw rate expected by the driver. If the difference between actual and expected yaw rates is substantial — that is, if the

direction of the vehicle's body will exceed the driver's expected line — the control unit signals the TCS control valve actu-

ator and PCM, thus reducing engine power and maintaining the expected line.

Rough Road Control

Based on signals from the wheel sensors, the control unit detects a rough road based on frequency of wheel rotational

vibration. The control unit then signals the TCS control valve actuator and PCM to relax engine power, thus improving

acceleration efficiency.

Grip Control

Based on signals about wheel speed and yaw rate, the control unit determines the efficiency of the grip of the tires on the

road and signals the TCS control valve actuator and PCM to relax engine power, if necessary, thus improving grip.

Main Control BlockProCarManuals.com

Engine Removal/Installation

Removal (cont'd)

7. Remove the battery cables from the under-hood fuse/

relay box.

BATTERY

CABLES

8.

9.
UNDER-HOOD

FUSE/RELAY BOX

Disconnect the engine wire harness connector on

the right (passenger's) side of the engine compart-

ment.

Remove the battery cable from the under-hood ABS

fuse/relay box.

BATTERY

CABLE

ENGINE WIRE

HARNESS

UNDER-HOOD ABS

FUSE/RELAY BOX
10. Remove the intake air duct and vacuum hose.

INTAKE AIR

DUCT

11.
VACUUM

HOSE

Remove the adjusting bolt, locknut and mounting

bolt, then remove the power steering (P/S) pump

belt and pump.

MOUNTING BOLT

10 x
1.25
mm

49 N-m (5.0 kgf-m, 36 Ibf-ft)

ADJUSTING

BOLT

P/S PUMP

BELT

LOCKNUT

8 x
1.25
mm

22 N-m (2.2 kgf-m,

16 Ibf-ft)ProCarManuals.com

System Descriptio n
This powe r steerin g syste m is speed-sensitive . It s mai n component s ar e a mechanica l spee d sensor , a rotar y valve-typ e
gearbox, an d a constan t volume , vane-typ e pump . Th e syste m regulate s th e powe r assis t accordin g to vehicl e speed , roa d
conditions , an d drivin g style . Th e amoun t o f powe r assis t change s linearl y fro m hig h assist , whe n drivin g a t lo w speed s o r
parking , t o lo w assist , whe n drivin g a t hig h speeds .
Fluid Flo w Diagra m
The flui d volum e fro m th e pump , whic h i s drive n b y th e cran k pulley , i s regulate d b y th e flo w contro l valv e buil t int o th e
pump . Th e regulate d flui d i s fe d t o th e valv e bod y uni t locate d outsid e th e pinio n shaf t o f th e steerin g gearbox . Th e flui d i s
regulate d t o th e prope r pressur e b y th e valve s i n th e valv e bod y uni t an d b y th e powe r steerin g spee d senso r befor e it
flow s t o th e powe r cylinder . Th e directio n o f th e flo w is determine d b y th e rotar y valve . Th e flui d the n returns to th e reser -
voi r throug h th e retur n passag e an d i s fe d t o th e pum p again .
To RESERVOI R
VALVE BOD Y UNI T
TORSIO N BA R
INPU T SHAF T
VALVE (SLEEVE )
RIGHT CYLINDE R PASSAG E
POWE R CYLINDE R
Steering Gearbo xLOW SPEE D FEE D PASSAG E
The steerin g gearbo x i s th e rack-and-pinio n type . Th e valv e bod y uni t consist s o f th e valv e bod y unit , wher e th e flui d pas -
sag e i s regulate d b y th e flui d pressure , an d th e assis t contro l valv e uni t whic h regulate s th e flui d passag e t o th e rotar y
valv e accordin g t o vehicl e speed .
ASSIST CONTRO L VALV E UNI T
STEERIN G RAC K VALV
E BOD Y UNI T
ToRESERVOI R
From PUM P
POWE R CYLINDE RCYLINDE
R LINE S ASSIS
T CONTRO L VALV E UNI T
PUM P
To POWE R STEERIN G
SPEE D SENSO R
PUM
P OUTLE T
HIGH-PRESSUR E
HIGH SPEE D
FEE D PASSAG E
POWER STEERIN G
SPEE D SENSO R
RESERVOI R
LEFT CYLINDE R
PASSAG E
ProCarManuals.com

One-way Valve (In Power Steering Speed

Sensor)

When the vehicle is moving at high speed, negative

pressure develops at the sensor inlet because the power

steering speed sensor is pumping faster than the fluid

can be supplied. To compensate for this, the outlet and

inlet ports are connected internally by a passage con-

taining a one-way valve that lets output fluid recirculate

to the inlet port to equalize pressure.

Driving at High Speed:

ONE-WAY VALVE
RESERVOIR

ROTORS
Relief Valve (In Power Steering Speed Sensor)

When the vehicle is moving in reverse, the power steer-

ing speed sensor also turns backward and pumps fluid

in the opposite direction. To avoid building up pressure

in the reaction chambers that would increase steering

effort while driving in reverse, the inlet and outlet-ports

are connected by a second internal passage containing a

relief valve that allows the fluid to recirculate.

Driving in Reverse:

RESERVOIR

RELIEF VALVEProCarManuals.com

System Description

System Operation (cont'd)

Hydraulic Control at Each Speed Range

When stopped:

When the vehicle is stopped with the engine idling, the fluid flow is shut off because the power steering speed sensor

rotor is not rotating. The standard pressure generated by the pressure control valve is applied to the assist control valve to

move the valve to the left. When the assist control valve is in this position, the orifice valve is closed. Therefore, the fluid

discharged from the pump is fed to the low speed valve of the valve body unit. Because the low speed valve has the small

chamfer and thereby the small opening angle, the large hydraulic pressure (steering rack thrust) results in the smallest

steering force (high assist).

HIGH SPEED FEED PASSAGE

LOW SPEED FEED PASSAGE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE

HIGH SPEED

VALVE

SLEEVE

TORSION BAR

INPUT SHAFT

VALVE BODY UNIT

SENSOR ORIFICE

ASSIST VOLUME: LIGHT

STEERING WITH VEHICLE PARKED

ROAD SURFACE RESISTANCE

SMALL
LARGE
FLOW: O (ZERO)

LOW SPEED

VALVE

POWER STEERING SPEED

SENSOR AT A STOP
RESERVOIR
PUMP
FULL CLOSE

PRESSURE CONTROL VALVE
(HIGH)
ASSIST CONTROL

VALVEProCarManuals.com

Middle speed range:

When the vehicle starts to move, the power steering speed sensor rotor starts to rotate as well, reducing the standard

pressure and generating the power steering speed sensor signal pressure. The valve returns to the right point where the

pressure of the power steering speed sensor signal equals the spring force of the assist control valve. When the assist

control valve is in this position, the orifice of the valve slightly opens.

Therefore, the fluid pressure from the pump is applied to the high speed valve of the valve body unit. Because the high

speed valve has a larger chamfer and the compound opening area with the low speed valve is larger than that when the

vehicle is stopped, the fluid pressure (steering rack thrust) is not generated unless the displacement angle is large (large

steering torque), resulting in moderately heavy steering (medium assist).

FLOW: MIDDLE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE (MEDIUM)

MIDDLE POWER STEERING SPEED

SENSOR ROTATION SPEED

MODERATELY HEAVY STEERING

IN MIDDLE SPEED RANGE
SMALL
ROAD SURFACE

RESISTANCE LARGE

High speed range:

When the vehicle is driven at high speed, the power steering speed sensor rotor rotates at a high speed, greatly reducing

the standard pressure. The pressure of the power steering speed sensor signal is at the lowest value, and the assist con-

trol valve is at the right end position.

When the assist control valve is in this position, the orifice of the valve opens fully. Therefore, the fluid pressure applied to

the high speed valve is larger than when the engine speed is at the middle speed range. The compound opening area with

the low speed valve is the largest this time, and the fluid pressure (steering rack thrust) is not generated unless the dis-

placement angle is very large (low assist).

FLOW: LARGE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE (LOW)

HIGH POWER STEERING SPEED

SENSOR ROTATION SPEED

LOW ASSIST: ADEQUATELY HEAVY

STEERING IN HIGH SPEED RANGE
SMALL
-ROAD SURFACE

RESISTANCE LARGE
PRESSURE CONTROL VALVE

SENSOR ORIFICE
HALF OPEN
ASSIST CONTROL

VALVE

VALVE BODY UNIT

ASSIST CONTROL

VALVE

FULL OPEN

SENSOR ORIFICE
PRESSURE CONTROL VALVEProCarManuals.com

Power Steering Hoses and Lines

Replacement

NOTE:

• Connect each hose to the corresponding line securely

until it contacts the stop on the line. Install the clamp

or adjustable clamp at the specified distance from the

hose end as shown.

• Add the recommended power steering fluid to the

specified level on the reservoir and check for leaks.
CAUTION: Check all clamps for deterioration and defor-

mation; replace the clamps with new ones if necessary.

ADJUSTABLE HOSE CLAMP:

HOSE CLAMP:

Slide the hose over the pipe until it contacts

the stop.
Slide the hose over the pipe until it contacts

the stop.

2.5-5.5 mm

(0.01
-
0.22
in)
2.0
-
4.0
mm

(0.08 -0.16
in)
2.5-5.5 mm

(0.01
-
0.22
in)

RESERVOIR

PUMP OUTLET LINE

(High-pressure)

11 N-m

(1.1 kgf-m, 8 Ibf-ft)

12 N-m (1.2 kgf-m, 9 Ibf-ft)

VALVE BODY UNIT

SENSOR RETURN LINE

PUMP

PUMP OUTLET LINE

(High-pressure)

RETURN HOSE
11 N-m (1.1 kgf-m,

8 Ibf-ft)
SENSOR OUTLET

HOSE
SENSOR INLET

HOSE

POWER STEERING

SPEED SENSOR
PUMP INLET HOSE

(Low-pressure)
SENSOR RETURN HOSE
RETURN HOSEProCarManuals.com

SUPPLEMENTAL RESTRAINT SYSTEMThe Acura TL SRS includes a driver's airbag located in the steering wheel hub and a passenger's airbag located in the dashboard above
the glove box. Information necessary to safely service the SRS is included in this Service Manual. Items marked with an asterisk (*) on
the contents page include, or are located near, SRS components. Servicing, disassembling or replacing these items will require special
precautions and tools, and should therefore be done by an authorized Honda dealer.
WARNING

To avoid rendering the SRS inoperative, which could lead to personal injury or death in the event of a severe frontal
collision, all SRS service work must be performed by an authorized Honda dealer.

Improper service procedures, including incorrect removal and installation of the SRS, could lead to personal injury
caused by unintentional activation of the front airbags, seat belt tensioners, and side airbags ('99-01 models).

Do not bump the SRS unit. Otherwise, the system may fail in a collision, or the airbags may deploy when the ignition
switch in ON (II).

All SRS electrical wiring harnesses are covered with yellow insulation. Related components are located in the steering
column, front console, dashboard, dashboard lower panel, in the dashboard above the glove box. Do not use electrical
test equipment on these circuits.
NOTE: The original radio has a coded theft protection circuit. Be sure to get the customer's code number before
± disconnecting the battery.
± removing the No. 39 (10A) fuse from the under±hood fuse/relay box.
± removing the radio.
After service, reconnect power to the radio and turn it on. When the word ºCODEº is displayed, enter the customer's 5-digit code to restore
radio operation.
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