Lexus SC300 / Lexus SC400. Manual - part 506

PRECAUTIONS

Before working on the fuel system, disconnect the cable
from 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: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ”LOCK” position and negative (–) terminal
cable is disconnected from the battery.

Do not smoke or work on open flame when working on
the fuel system.

Keep gasoline away from rubber or leather parts.

INSPECTION PRECAUTIONS

MAINTENANCE PRECAUTIONS

CHECK CORRECT ENGINE TUNE–UP
(See page

EM–8

)

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 terminals

and all other ignition system lines are reconnected
securely.

(d) When cleaning the engine compartment, be especially

careful to protect the electrical system from water.

PRECAUTIONS WHEN HANDLING OXYGEN SENSOR
(a) Do not allow oxygen sensor to drop or hit against an

object.

(b) Do not allow the sensor to come into contact with water.

FI–12

– Precautions, Inspection Precautions

EFI SYSTEM

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.

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.

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

Separation of the engine oil dipstick, oil filler cap, PCV hose,
etc. may cause the engine to run out of tune.

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

Before removing EFI wiring connectors, terminals, etc., first
disconnect 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.

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.

Do not open the ECU cover.

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.

Parts should be replaced as an assembly.

FI–13

EFI SYSTEM – Inspection Precautions

8. Care is required when pulling out and inserting wiring

connectors.
(a) Release the lock and pull out the connector, pulling on

the connectors.

(b) Fully insert the connector and check that it is locked.

When inspecting a connector with a volt/ohmmeter.
(a) Carefully take out the water–proofing rubber if it is a

water–proof type connector.

(b) Insert the test probe into the connector from wiring side

when checking the continuity, amperage or voltage.

connector securely.

10. Use SST for inspection or test of the injector, cold start

injector or its wiring connector.

SST 09842–30055 (A) and 09842–30070 (C)

FI–14

EFI SYSTEM – Inspection Precautions

FUEL SYSTEM

1. When disconnecting the high fuel pressure line, a large

amount of gasoline will spill out, so observe the following
procedures:
(a)  Put a container under the connection.
(b)  Slowly loosen the connection.
(c)  Disconnect the connection.
(d)  Plug the connection with a rubber plug.

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: 15 N

⋅

m (150 kgf

⋅

cm, 11 ft

⋅

lbf)

(Flare Nut Type)
(a) Apply

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

⋅

m (310 kgf

⋅

cm, 22 ft

⋅

lbf)

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.

installing–never use engine, gear or brake oil.

4. Install the injector to delivery pipe and cylinder head as

shown in the illustration.

FI–15

EFI SYSTEM – Inspection Precautions

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