1991 LEXUS SC400 engine

Ignition Main Relay
INSPECTION OF IGNITION MAIN RELAY
1. REMOVE IGNITION MAIN RELAY FROM RELAY BOX INENGINE COMPARTMENT
2. INSPECT IGNITION MAIN RELAY
A. Inspect relay continuity (a) Using an ohmmeter, check that there is continuity
between terminals 3 and 6.
(b) Check that there is continuity between terminals 4 and 5.
(c) Check that there is no continuity between terminals 1 and 2.
If continuity is not as specified, replace the relay.
B. Inspect relay operation (a) Apply battery voltage across terminals 3 and 6.
(b) Using an ohmmeter, check that there is continuitybetween terminals 1 and 2.
(c) Apply battery voltage across terminals 4 and 5.
(d) Check that there is continuity between terminals 1 and 2.
If operation is not as specified, replace the relay.
3. REINSTALL IGNITION MAIN RELAY
FI±86
± Electronic Control System (Igniti\
on Main Relay)EFI SYSTEM
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INSPECTION OF EGR GAS
TEMPERATURE SENSOR
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and the negative (±) termi-
nal cable is disconnected from the battery.
2. DRAIN ENGINE COOLANT
3. REMOVE EGR VALVE (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the following hoses from the EGR valve:(1) Water by±pass hose (from ISC valve)
(2) Water by±pass hose (from rear water by±pass joint)
(c) Remove the two nuts, EGR valve and gasket.
4. REMOVE EGR VALVE ADAPTOR (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the PCV hose from the EGR valve adaptor.
(c) Remove the two bolts, two nuts, EGR valve adaptor andgasket. FI±103
EFI SYSTEM
± Electronic Control System (EGR Gas Temperature Sensor (USA Spec. only))
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9. REINSTALL EGR VALVE(a) Place a new gasket on the EGR valve adaptor.
NOTICE:
w Do not touch the adaptor and EGR valve surfaces of the
gasket with your hand.
w Align the port holes of the gasket and adaptor. Be careful
of the installation direction.
(b) Install the EGR valve with the two nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(c) Connect the following hoses to the EGR valve:
(1) Water by±pass hose (from ISC valve)
(2) Water by±pass hose (from rear water by±pass joint)
(d) Connect the EGR gas temperature sensor.
10. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
11. REFILL WITH ENGINE COOLANT FI±105
EFI SYSTEM
± Electronic Control System (EGR Gas Temperature Sensor (USA Spec. only))
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INSPECTION OF KNOCK SENSORS
1. REMOVE AIR INTAKE CHAMBER(See steps 1 to 16 on pages FI±27 to 32)
2. DISCONNECT FUEL INLET HOSE FROM LH DELIVERY PIPE
Remove the pulsation damper and two gaskets, and discon-
nect the inlet hose.
3. DISCONNECT FUEL RETURN HOSE FROM FUEL RETURN PIPE
4. DISCONNECT EGR PIPE FROM RH CYLINDER HEAD Remove the bolt holding the EGR pipe to the cylinder head,
and disconnect the EGR pipe.
5. DISCONNECT ENGINE WIRE FROM INTAKE MANIFOLD Remove the two bolts, and disconnect the engine wire.
6. DISCONNECT ENGINE WIRE FROM DELIVERY PIPES, REAR WATER BY±PASS JOINT AND RH CYLINDER
HEAD
(a) Remove the four bolts holding the engine wire to thedelivery pipes, and disconnect the engine wire from the
delivery pipe.
(b) Remove the two bolts holding the engine wire to the rear
water by±pass joint, and disconnect the engine wire
from the rear water by±pass joint.
(c) Remove the two bolts holding the engine wire to the rear
side of the RH cylinder head, and disconnect the engine
wire from the RH cylinder head.
FI±108
EFI SYSTEM
± Electronic Control System (Knock Sensors)
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(d) Disconnect the two engine wire connectors from theconnector bracket on the front side of the LH delivery
pipe.
(e) Disconnect the eight injector connectors.
7. REMOVE FUEL RETURN PIPE (a) Remove the bolt holding the return pipe to the LHcylinder head.
(b) Remove the union bolt, two gaskets and return pipe.
8. REMOVE DELIVERY PIPES AND INTAKE MANIFOLD ASSEMBLY
(a) Remove the six bolts and four nuts holding the intakemanifold to the cylinder heads.
(b) Remove the two delivery pipes and intake manifold assembly.
(c) Remove the two intake manifold gaskets.
9. REMOVE KNOCK SENSOR (a) Disconnect the knock sensor connectors
(b) Using SST, remove the two knock sensors.
SST 09816±30010
10. INSPECT KNOCK SENSOR Using an ohmmeter, check that there is no continuity be-
tween the terminal and body.
If there is continuity, replace the sensor. FI±109
EFI SYSTEM
± Electronic Control System (Knock Sensors)
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11. REINSTALL KNOCK SENSOR(a) Using SST, remove the two knock sensors.
SST 09816±30010
Torque: 44 N Vm (450 kgf Vcm, 33 ft Vlbf)
(b) Connect the knock sensor connectors.
12. REINSTALL DELIVERY PIPES AND INTAKE MANIFOLD ASSEMBLY
(a) Place two new gaskets on the cylinder heads with thewhite painted mark facing upward.
NOTICE: Align the port holes of the gasket and cylinder
head. Be careful of the installation direction.
(b) Place the delivery pipes and intake manifold assembly in position on the cylinder heads with the arrow mark on
the intake manifold facing forward.
NOTICE: Be careful of the installation direction.
(c) Install the six mounting bolts and four mounting nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolts 30 mm (1.18 in.) in length.
13. REINSTALL FUEL RETURN PIPE Install the return pipe with two new gaskets, union bolt and
bolt.
Torque (Union bolt):
35 NVm (360 kgf Vcm, 26 ft Vlbf)
14. REINSTALL ENGINE WIRE TO DELIVERY PIPES, REAR
WATER BY±PASS JOINT AND RH CYLINDER HEAD
(a) Connect the eight injector connectors.
(b) C onnect the two engine wire connectors to the
connector bracket on the LH delivery pipe.
FI±110
EFI SYSTEM
± Electronic Control System (Knock Sensors)
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(c) Install the engine wire to the RH cylinder head with thetwo bolts.
(d) Install the engine wire to the rear water by±pass joint with the two bolts.
(e) Install the engine wire to the delivery pipes with the four bolts.
15. REINSTALL ENGINE WIRE TO INTAKE MANIFOLD Install the engine wire with the two bolts.
16. TEMPORARILY REINSTALL EGR PIPE TO RH CYLINDER
HEAD
Temporarily Install the EGR pipe with the bolt.
17. RECONNECT FUEL RETURN HOSE TO FUEL RETURN PIPE
18. RECONNECT FUEL INLET HOSE TO LH DELIVERY PIPE
Using SST, connect the inlet hose with two new gaskets and
pulsation damper.
SST 09612±24014 (09617±24011)
Torque: 39 N Vm (400 kgf Vcm, 29 ft Vlbf)
33 N Vm (340 kgf Vcm, 24 ft Vlbf) for SST
HINT: Use a torque wrench with a fulcrum length of 30 cm
(11.81 in.). FI±111
EFI SYSTEM
± Electronic Control System (Knock Sensors)
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Main Oxygen Sensors
INSPECTION OF MAIN OXYGEN
SENSORS
1. WARM UP ENGINEAllow the engine to warm up to normal operating
temperature.
2. INSPECT FEEDBACK VOLTAGE Connect the positive (+) probe of a voltmeter to terminal VF1
(for LH bank) or VF2 (for RH bank) of the check (ºDIAGNO-
SISº) connector, and negative (±) probe to terminal E1. Per-
form the test as follows described on the next page.
HINT: Use SST when connecting between terminals TE1 and
E1 of the check connector.
SST 09843±18020 FI±113
± Electronic Control System (\
Main Oxygen Sensors)EFI SYSTEM
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