1991 LEXUS SC400 engine

ELECTRONIC CONTROL SYSTEM
The control system consists of sensors which detect various engine conditions, and a ECU which deter\
-
mines the injection volume (timing) based on the signals from the sens\
ors.
The various sensors detect the air intake volume, engine rpm, oxygen densit\
y in the exhaust gas, coolant
temperature, air intake temperature and atmospheric pressure etc. and convert the in\
formation into an electrical
signal which is sent to the ECU. Based on these signals, the ECU calculates th\
e optimum ignition timing for the
current conditions and operates the injectors.
The ECU not only controls the fuel injection timing, but also the self diag\
nostic function which records the
occurrence of a malfunction, ignition timing control, idle rpm control, \
EGR control, EVAP control, fuel pressure
control and fuel pump control. FI±9
EFI SYSTEM
± Operation
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PREPARATION
SST (SPECIAL SERVICE TOOLS)
IllustrationPart No.Part NameNote
09268±41045Injection Measuring
Tool Set
(09268±41090)(No. 7 Union)
Injector
(09268±52010)(Injection Measuring
Attachment)
Injector
(09405±09015)(No. 1 Union)
Injector
09268±45012EFI Fuel Pressure
Gauge
09612±24014
Steering Gear
Housing Overhaul
Tool Set
(09617±24011(Steering Rack Wrench)
Fuel pressure pulsation damper
09631±22020
Power Steering
Hose Nut 14 x 17 mm
Wrench SetFuel line flare nut
09816±30010Oil Pressure
Switch Socket
Knock sensor
09842±30070Wire ªFº
EFI Inspection
Injector
09843±18020Diagnosis Check
Wire
09990±01000
Engine Control
Computer Check
Harness ªAº
±
EFI SYSTEM PreparationFI±9
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RECOMMENDED TOOLS
IllustrationPart No.Part NameNote
09082±00015TOYOTA
Electrical Tester
09200±00010Engine Adjust
Kit
09258±00030Hose Plug Set
Plug for the vacuum hose, fuel hose, etc.
EQUIPMENT
Part NameNote
Graduted cylinderInjector
Tachometer
Torque wrench
Soft brush
Carburetor cleanerThrottle body
StethoscopeInjector
Vacuum gauge
EQUIPMENT
Part NameNote
Graduted cylinderInjector
Tachometer
Torque wrench
Soft brush
Carburetor cleanerThrottle body
StethoscopeInjector
Vacuum gauge
FI±10±
EFI SYSTEM Preparation
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Preparation
SST (SPECIAL SERVICE TOOLS)
IllustrationPart No.Part NameNote
09268±41045Injection Measuring
Tool Set
(90268±41070)No. 4 Union
Injector
(09268±41080)No. 6 Union
Cold start Injector
(09268±52010)Injection Measuring
Attachment
Injector
09268±45012EFI Fuel Pressure
Gauge
09612±24014
Steering Gear
Housing Overhaul
Tool Set
(09617±24011)Steering Rack Wrench
Fuel pressure pulsation damper
09631±22020
Power Steering
Hose Nut 14 X 17 mm
Wrench SetFuel line flare nut
09816±30010Oil Pressure
Switch SocketKnock sensor
09842±30055Wire ªGº
EFI Inspection
Cold start Injector
09842±30070Wire ªFº
EFI Inspection
Injector
09843±18020Diagnosis Check
Wire
0990±01000
Engine Control
Computer
Check Harness ªAº
FI±10 ± PreparationEFI SYSTEM
WhereEverybodyKnowsYourName

RECOMMENDED TOOLS
IllustrationPart No.Part NameNote
09082±0015TOYOTA
Electrical Tester
09200±00010Engine Adjust
Kit
09258±00030Hose Plug Set
Plug for the Vacuum hose, fuel hose ect.
EQUIPMENT
Part NameNote
Graduated cylinderInjector
Tachometer
Torque wrench
SSM (SERVICE SPECIAL MATERIALS)
Part NamePart No.Use etc.
Seal packing 1282B,08826±00100Water inlet housing
Three bond 1282B or equivalent
FI±11EFI SYSTEM ± Preparation
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PRECAUTIONS
1. Before working on the fuel system, disconnect the cablefrom negative (±) terminal of the battery.
HINT: Any diagnostic code retained by the computer will be
erased when the battery terminal is removed. Therefore, if
necessary, read the diagnosis before removing the battery
terminal.
CAUTION: Turn the ignition switch to ºLOCKº. Discon-
nect the cable from the negative (±) terminal of the bat-
tery. Wait at least 20 seconds before proceeding with
work.
2. Do not smoke or work on open flame when working on the fuel system.
3. Keep gasoline away from rubber or leather parts.
INSPECTION PRECAUTIONS
MAINTENANCE PRECAUTIONS
1. CHECK CORRECT ENGINE TUNE±UP (See page EM±8)
2. PRECAUTIONS WHEN CONNECTING GAUGE (a) Use the battery as the power source for the timing light,tachometer, etc.
(b) Connect the test probe of a tachometer to the terminal IG
of the check connector.
3. IN EVENT OF ENGINE MISFIRE, FOLLOWING PRECAUTIONS SHOULD BE TAKEN
(a) Check proper connection of battery terminals, etc.
(b) Handle high±tension cords carefully.
(c) After repair work, check that the ignition coil terminalsand all other ignition system lines are reconnected
securely.
(d) When cleaning the engine compartment, be especially careful to protect the electrical system from water.
4. PRECAUTIONS WHEN HANDLING OXYGEN SENSOR (a) Do not allow oxygen sensor to drop or hit against anobject.
(b) Do not allow the sensor to come into contact with water.
±
EFI SYSTEM Precautions, Inspection PrecautionsFI±11
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IF VEHICLE IS EQUIPPED WITH MOBILE
RADIO SYSTEM (HAM, CB, ETC.)
The ECU has been designed so that it will not be affected by out-
side interference. However, if your vehicle is equipped with a CB
radio transceiver, etc. (even one with about 10 W output), it may,
at times, have an effect upon ECU operation, especially if the an-
tenna and feeder are installed nearby.
Therefore, observe the following precautions:
1. Install the antenna as far away as possible from the ECU. The ECU is located on the floor panel on the passenger side
so the antenna should be installed at the rear of the vehicle.
2. Keep the antenna feeder as far away as possible from the ECU wires±at least 20 cm (7.87 in.) ±and, especially, do not
wind them together.
3. Check that the feeder and antenna are properly adjusted.
4. Do not equip your vehicle with a powerful mobile radio
system.
5. Do not open the cover or the case of the ECU unless absolutely necessary. (If the IC terminals are touched, the IC
may be destroyed by static electricity.)
AIR INDUCTION SYSTEM
1. Separation of the engine oil dipstick, oil filler cap, PCV hose,
etc. may cause the engine to run out of tune.
2. Disconnection, looseness or cracks in the parts of the air
induction system between the throttle body and cylinder
head will cause air suction and cause the engine to run out
of tune.
ELECTRONIC CONTROL SYSTEM
1. Before removing EFI wiring connectors, terminals, etc., firstdisconnect the power by either turning the ignition switch
OFF or disconnecting the battery terminals.
HINT: Always check the diagnosis code before disconnecting
the battery terminals.
2. When installing the battery, be especially careful not to
incorrectly connect the positive (+) and negative (±) cables.
3. Do not permit parts to receive a severe impact during removal or installation. Handle all EFI parts carefully, especially the
ECU.
4. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact
can cause further troubles.
5. Do not open the ECU cover.
6. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment,
prevent water from getting on the EFI parts and wiring
connectors.
7. Parts should be replaced as an assembly.
FI±12
±
EFI SYSTEM Inspection Precautions
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FUEL SYSTEM
1. When disconnecting the high fuel pressure line, a largeamount of gasoline will spill out, so observe the following
procedures:
(a) Remove the luggage compartment trim cover.
(b) Disconnect the fuel pump connector.
(c) Start the engine, After the engine has stopped on itsown, turn off the ignition switch.
(d) Put a container under the connection.
(e) Slowly loosen the connection.
(f) Disconnect the connection.
(g) Plug the connection with a rubber plug.
(h) Reconnect the fuel pump connector.
(i) Reinstall the luggage compartment trim cover.
2. When connecting the flare nut or union bolt on the high pressure pipe union, observe the following procedures:
(Union Bolt Type)
(a) Always use a new gasket.
(b) Tighten the union bolt by hand.
(c) Tighten the union bolt to the specified torque.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
(Flare Nut Type)
(a) Apply a light coat of engine oil to the flare nut and tighten
the flare nut by hand.
(b) Using SST, tighten the flare nut to specified torque.
SST 09631±22020
Torque: 30 N Vm (310 kgf Vcm, 22 ft Vlbf)
HINT: Use a torque wrench with a fulcrum length of 30 cm
(11.81 in.).
3. Observe the following precautions when removing and installing the injectors.
(a) Never reuse the O±ring.
(b) When placing a new O±ring on the injector, take care not
to damage it in any way.
(c) Coat a new O±ring with spindle oil or gasoline before installing±never use engine, gear or brake oil.
FI±14
±
EFI SYSTEM Inspection Precautions
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