ECU LEXUS SC400 1991 Service Repair Manual

STEERING GEAR HOUSING
DISASSEMBLY
SR0GL±02
1. CLAMP GEAR HOUSING IN VISEUsing SST, secure the steering gear in a vise.
SST 09612±00012
2. REMOVE RIGHT AND LEFT TURN PRESSURE TUBES
(a) Remove the union bolt and gaskets.
(b) Using SST, remove the pressure tube. SST 09633±00020
(c) Remove the union seat.
3. REMOVE TIE ROD ENDS
(a) Loosen the lock nut and place matchmarks on the tie rod end
and rack end.
(b) Remove the tie rod end and rack guide spring cap lock nut.
4. REMOVE RACK BOOTS, CLAMPS AND CLIPS
(a) Remove the clip and clamp.
(b) Remove the rack boot.
(c) Mark the left and right boot.
5. REMOVE RACK ENDS AND CLAW WASHERS
(a) Unstake the claw washer.
NOTICE: Avoid any impact to the rack.
SR±150±
STEERING POWER STEERING
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ELECTRONIC CONTROL SYSTEM
PRECAUTION
SR0GR±01
Do not open the cover or the case of the ECU and various computers unless \
absolutely necessary.
(If the IC terminals are touched, the IC may be destroyed by static ele\
ctricity.)
ELECTRONIC CIRCUIT
SR0GS±04
±
STEERING POWER STEERINGSR±163
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TROUBLESHOOTING FLOW±CHART
SR0GT±04
Trouble

Hard steering at idle or low±speed driving.

Steering too sensitive during high±speed driving.
Preliminary Check

Check tire pressure.

Check lubrication of suspension and steering linkage.

Check front wheel alignment.

Check steering system joint and suspension arm ball joint.

Check for bent steering column.

Check that all connectors are secure.

Check PS pump fluid pressure. (See page SR±115)
SR±164±
STEERING POWER STEERING
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POWER STEERING ECU
1. JACK UP VEHICLE AND SUPPORT IT ON STANDS
2. START ENGINE
3. MEASURE VOLTAGE OF ECU
(a) Using a voltmeter, measure the voltage between ECUterminals SOL  and GND while the engine is idling.
Standard voltage:
0.3±0.5 V
(b) Place the transmission in gear and while running at about 37
mph (60 km/h), measure the voltage between ECU terminals
SOL  and GND.
Standard voltage:
Voltage measured in (a) above, minus
(IUZ±FE Engine)
0.07±0.02 V
(2JZ±FE Engine)
0.05±0.18 V
If no voltage, try another ECU.
4. LOWER VEHICLE
SR±168
±
STEERING POWER STEERING
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STEERING COLUMN
DESCRIPTION
SR0EA±02
There are two types of steering column, the manual tilt/manual telescopic one\
, and the power tilt/power
telescopic one.
SR0EB±02
OPERATION
POWER TILT OPERATIONThe power tilt mechanism consists of the control gear assembly, tilt motor, tilt position sensor, tilt and tele-
scopic switch, unlock warning switch and tilt and telescopic ECU.
The control gear assembly consists of the worm wheel, tilt gear, tilt worm and slider. Rotation of the tilt motor
moves the slider towards the tilt worm. The column upper tube is integrated w\
ith the slider and is rotated
up and down by movement of the slider.
SR±4
±
STEERING STEERING COLUMN
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POWER TELESCOPIC OPERATION
SR0EC±02
The power telescopic mechanism is composed of the control gear assembly, telescopic motor, telescopic
position sensor, tilt and telescopic switch, unlock warning switch and tilt and telesco\
pic ECU.
The control gear assembly is composed of the worm wheel, telescopic scre\
w and slider. Rotation of the
telescopic motor moves the slider in the direction of the telescopic screw axis. The\
sliding tube is integrated
with the slider and is moved forward and backward by movement of the slider.
±
STEERING STEERING COLUMNSR±5
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19. REMOVE UPPER COLUMN TUBE
(a) Set SST, the nut (10 mm diameter, 1.25 mm pitch), platewasher (36 mm outer diameter) and bolt (10 mm diameter,
1.25 mm pitch, 50 mm length), as shown.
And then remove the 2 tilt steering bolts.
SST 09910±00015 (09911±00011, 09912±00010)
(Reference)
Nut 90170±10004
Plate washer 90201±10201
Bolt 91111±51050
(b) Remove the upper column tube from the lower column tube.
20. REMOVE TILT MEMORY BOLT Using a hexagon wrench, remove the tilt memory bolt and
square nut.
21. REMOVE MAIN SHAFT ASSEMBLY
(a) Secure the column upper tube in a vise. NOTICE: Do not tighten the vise too tight.
(b) Using SST, compress the compression spring. SST 09950±20017 (09956±00010)
(c) Using snap ring pliers, remove the snap ring.
SR±18
±
STEERING STEERING COLUMN
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(c) Remove the upper tube and main shaft from the lower tube.
12. REMOVE TILT STEERING HOUSING SUPPORT
13. REMOVE MAIN SHAFT ASSEMBLY
(a) Secure the column upper tube in a vise.
NOTICE: Do not tighten the vise too tight.
(b) Using SST, compress the compression spring.SST 09950±20017 (09956±00010)
(c) Using snap ring pliers, remove the snap ring.
(b) Remove the main shaft from the upper tube.
(c) Remove the spring, thrust collar and bearing.
STEERING COLUMN INSPECTION AND
REPLACEMENT
SR0EM±03
1. INSPECT KEY CYLINDER Check that the steering lock mechanism operates properly.
SR±32
±
STEERING STEERING COLUMN
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DESCRIPTION
By operating the driving position memory and return switch the driver's seat, steering wheel and outer mir-
ror are moved to their respective memorized positions.
 

Parts Name\
 
\

\
Function 




Tilt & Telescopic ECU
\
 
\


\

\

Control the manual operation, return operation and memory and return ope\
ration for tilt
and telescopic of steering wheel.
 Auto Set Switch\
 \
This switch is a main switch for the away operation of tilt and telescop\
ic.
 




Manual Switch\
 
\


\

\

This switch is an operation switch to operate tilt and telescopic manual\
ly. When one of tilt
up, tilt down, telescopic Extension and telescopic Contraction is operat\
ed, steering wheel
will be able to set on the optional position within the extent of operat\
ing.
 


Driving Position
Memory and
Return Switch\
 
\

\

Operating this switch makes return operation that driver seat steering w\
heel and outer mirror
are set on the memorized position working together power seat and outer \
mirror.
 

Position Sensor
\
 
\

\
Tilt position sensor detect an amount of tilt and input it to ECU.
Telescopic position sensor detect an amount of slide and input it to ECU.\
 

Motor
\
 
\

\
There is a tilt motor and telescopic motor respectively. These are operated by a signal from
the ECU.
SR±40±
STEERING STEERING COLUMN
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HOW TO PROCEED WITH TROUBLESHOOTING
Perform troubleshooting in accordance with the procedure on the following page.\

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, obtain as much detail as possible about
the problem.
 PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem, using
the ªProblem Simulation Methodsº.
 MATRIX CHART OF PROBLEM SYMPTOMS
Confirm the order of inspection for each applicable problem symptom on t\
he matrix chart after first fully
confirming the scope of the problem symptoms. For example, if the tilt operation i\
s not working, check
whether the tilt is not working in manual, auto and return, and also check if the telescopic, seat or mirror
operation is not working in addition to the tilt operation.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection order \
confirmed in . Judge
whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or the ECU.
6 REPAIR
After the cause of the problem is located, perform repairs by following the i\
nspection and replacement pro-
cedures in this manual.
7 CONFIRMATION TEST After completing repairs, confirm not only that the malfunction is eliminated,\
but also seat and mirror opera-
tions are normal.
SR±45
SR±52
SR±62 ~ SR±101 IN±26
SR±44
±
STEERING STEERING COLUMN
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