1991 LEXUS SC400 engine

OKNG
NGOK
NGOK
OKNG
INSPECTION PROCEDURE
1Check operation of brake warning light.
Check that the brake warning light in the instrument panel comes on when the \
parking brake is opera-
tion with the engine running, and the light goes off when the parking brake is not operating.C
Check brake warning light circuit.
2Input signal check.
C
OK
1. See input signal check.
2. Check the indicator light when the parking brake isoperating.
The indicator light goes off when the parking brake
is operating.
Proceed to next circuit inspection shown on matrix
chart.
3Check voltage between terminal PKB of tilt & telescopic ECU connector and bod\
y ground.
C
OK
PRemove tilt & telescopic ECU with connectors still con-
nected.
1. Turn ignition switch ON.
2. Measure voltage between terminal PKB of tilt & telescopic ECU connector and body ground, when
the parking brake lever is operating.
Proceed to next circuit inspection shown on matrix
chart.
4Check for open in harness and connector between tilt & telescopic ECU and brak\
e warning light
(See page IN±33).
.
Repair or replace harness or connector
Check and replace tilt & telescopic ECU.
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STEERING STEERING COLUMNSR±97
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POWER STEERING
DESCRIPTION
SR0KG±03
The Progressive Power Steering (PPS) is basically a power rack and pinion\
gear with a rotary control valve.
The PPS varies the amount of hydraulic assistance with respect to vehicle r\
oad speed. In addition the unit
incorporates an electronically controlled hydraulic reaction chamber.
PRINCIPLES OF POWER STEERING
Power steering is a hydraulic device which utilizes engine power to reduce ste\
ering effort. Consequently,
the engine is used to drive a pump to develop fluid pressure, and this p\
ressure acts on a piston within the
power cylinder so that the piston assists the rack effort. The amount of this assistance depends on the ex-
tent of pressure acting on the piston. Therefore, if more steering force is \
required, the pressure must be
raised. The variation in the fluid pressure is accomplished by a control valve \
which is linked to the steering
main shaft.
SR±102
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STEERING POWER STEERING
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IDLE±UP DEVICE
The pump produces the maximum fluid pressure when the steering wheel is tur\
ned fully to the right or left
and, at this time, there is a maximum load on the pump which causes a decrea\
se in engine idle rpm. To
solve this problem, vehicles are equipped with an idle±up device which acts to raise the engine idle rpm
whenever there is a heavy load on the pump.
On EFI engines, when the piston of the air control valve is pushed by fl\
uid pressure, the air valve opens
and the volume of air by±passing the throttle valve is increased to r\
egulate engine rpm.
The idle±up device functions to raise engine idle rpm when pump fluid pr\
essure acts on the air control valve,
installed to the pump body, to control the flow of air.
SR±108
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ON±VEHICLE INSPECTION
CHECK IDLE±UP
SR0FZ±04
1. WARM UP ENGINE
2. TURN AIR CONDITIONER SWITCH OFF
3. CHECK IDLE±UP
(a) Fully turn the steering wheel.
(b) Check that the engine rpm decreases when the air controlvalve hose is pinched.
(c) Check that the engine rpm increases when the air control valve hose is released.
FLUID LEVEL CHECK
SR0G0±03
1. KEEP VEHICLE LEVEL
2. BOOST FLUID TEMPERATUREWith the engine idling at 1,000 rpm or less, turn the steering
wheel from lock to lock several times to boost fluid tempera-
ture.
Fluid temperature:
805C (176 5F)
3. STOP ENGINE
4. CHECK FOR FOAMING OR EMULSIFICATION
HINT: Foaming and emulsification indicate either the exis-
tence of air in the system or that the fluid level is too low.
5. CHECK FLUID LEVEL IN OIL RESERVOIR Check the fluid level and add fluid if necessary.
Fluid:
ATF DEXRON
[ II
HINT: Check that the fluid level is within the HOT LEVEL of
the dipstick of the reservoir cap. If the fluid is cold, check that
it is within the COLD LEVEL of the dipstick.
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STEERING POWER STEERINGSR±113
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POWER STEERING FLUID
REPLACEMENT
SR0G1±04
1. JACK UP FRONT OF VEHICLE AND SUPPORT IT WITHSTANDS
2. REMOVE FLUID RETURN HOSE FROM OIL RESERVOIR AND DRAIN FLUID INTO CONTAINER
NOTICE: Take care not to spill fluid on the drive belt.
3. TURN STEERING WHEEL FROM LOCK TO LOCK WHILEDRAINING FLUID
4. FILL OIL RESERVOIR WITH FRESH FLUID
Fluid: ATF DEXRON
[ II
5. START ENGINE AND RUN IT AT 1,000 RPMAfter 1 or 2 seconds, fluid will begin to discharge from the re-
turn hose. Stop the engine immediately at this time.
NOTICE: Take care that some fluid remains left in the oil reser-
voir.
6. REPEAT STEPS 4 AND 5 FOUR OR FIVE TIMES UNTIL THERE IS NO MORE AIR IN FLUID
7. CONNECT RETURN HOSE TO OIL RESERVOIR
8. BLEED POWER STEERING SYSTEM (See page SR±115)
SR±114
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POWER STEERING SYSTEM BLEEDING
SR0G2±04
1. CHECK FLUID LEVEL IN OIL RESERVOIRCheck the fluid level and add fluid if necessary.
Fluid:
ATF DEXRON
[ II
HINT: Check that the fluid level is within the HOT LEVEL of
the dipstick of the reservoir cap. If the fluid is cold, check that
it is within the COLD LEVEL of the dipstick.
2. START ENGINE AND TURN STEERING WHEEL FROM LOCK TO LOCK 3 OR 4 TIMES
With the engine speed below 1,000 rpm, turn the steering
wheel to left or right full lock and keep it there for 2±3 se-
conds, then turn the wheel to the opposite full lock and keep
it there for 2±3 seconds.
3. CHECK THAT FLUID IN OIL RESERVOIR IS NOT FOAMY OR CLOUDY AND DOES NOT RISE OVER MAXIMUM
WHEN ENGINE IS STOPPED
Measure the fluid level with the engine running. Stop the en-
gine and measure the fluid level.
Maximum rise:
5 mm (0.20 in.)
If a problem is found, repeat fluid replacement on page
SR±114. Rep air the PS if the problem persists.
OIL PRESSURE CHECK
SR0G3±03
1. CONNECT PRESSURE GAUGE
(a) Using SST, disconnect the pressure line joint.SC 400:
SST 09631±22020
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STEERING POWER STEERINGSR±115
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(b) Connect the gauge side of the pressure gauge to the PSpump side, and the valve side to the gear housing side.
2. BLEED POWER STEERING SYSTEM (See page SR±115)
3. START ENGINE AND RUN IT AT IDLE
4. BOOST FLUID TEMPERATURE With the engine idling at 1,000 rpm or less, turn the steering
wheel from lock to lock several times to boost fluid tempera-
ture.
Fluid temperature: 80
C (176
F)
5. CHECK FLUID PRESSURE READING WITH VALVE
CLOSED
Close the pressure gauge valve and observe the reading on
the gauge.
Minimum pressure:
7,355 kPa (75 kgf/cm
2, 1,067 psi)
NOTICE:
w Do not keep the valve closed for more than 10 seconds.
w Do not let the fluid temperature become too high.
If pressure is low, repair or replace the PS vane pump.
6. OPEN VALVE FULLY
7. CHECK AND RECORD PRESSURE READING AT 1,000
RPM
8. CHECK AND RECORD PRESSURE READING AT 3,000 RPM
Check that the pressure difference between the 1,000 rpm
and 3,000 rpm checks is less than 490 kPa (5 kgf/cm
2, 71
psi). If the difference is excessive, repair or replace the flow
control valve of the PS vane pump.
NOTICE: Do not operate the steering wheel.
SR±116±
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9. CHECK PRESSURE READING WITH STEERING WHEELTURNED TO FULL LOCK
Be sure the pressure gauge valve is fully opened and the en-
gine idling.
Minimum pressure:
7,355 kPa (75 kgf/cm
2, 1,067 psi)
NOTICE:
w Do not maintain lock position for more than 10 seconds.
w Do not let the fluid temperature become too high.
If pressure is low, the gear housing has an internal leak and
must be repaired or replaced.
10. MEASURE STEERING EFFORT
(a) Center the steering wheel and run the engine at idle.
(b) Using a spring scale, measure the steering effort in both directions.
Maximum steering effort:
40 N (4.1 kgf, 9.0 lbf)
If steering effort is excessive, repair the power steering unit.
HINT: Be sure to consider the tire type, pressure and contact
surface before making your diagnosis.
(c) Disconnect the solenoid connector.
(d) Using a spring scale, measure the steering effort in both directions.
(Reference)
Maximum steering effort:
76 N (7.7 kgf, 17.0 lbf)
If steering effort is not heavier than (b), check solenoid.
HINT: Be sure to consider the tire type, pressure and contact
surface before making your diagnosis.
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STEERING POWER STEERINGSR±117
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