Lexus SC300 / Lexus SC400. Manual - part 505

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., 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.

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

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.

9. 

Use SST for inspection or test of the injector or its wiring
connector.
SST 09842–30070

–

EFI SYSTEM

Inspection Precautions

FI–13

FUEL SYSTEM

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

amount 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 its

own, 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

⋅

m (350 kgf

⋅

cm, 25 ft

⋅

lbf)

(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

⋅

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.

(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

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

shown in the illustration.

5.  Check that there are no fuel leaks after performing any

maintenance on the fuel system.
(a)  Using SST, connect terminals +B and FP of the check

(”DIAGNOSIS”) connector.

SST 09843–18020
(b)  With engine stopped, turn the ignition switch ON.

(c)  When the fuel return hose is pinched, the pressure

within high pressure line will rise to approx. 392 kPa (4
kgf/cm2, 57 psi). In this state, check to see that there are
no leaks from any part of the fuel system.

NOTICE: Always pinch the hose. Avoid bending as it may
cause the hose to crack.

(d)  Turn the ignition switch OFF.
(e)  Remove SST from the check connector.
SST 09843–18020

–

EFI SYSTEM

Inspection Precautions

FI–15