ignition LEXUS SC300 1991 Service Repair Manual

COMPONENTS
REMOVAL OF AIR FLOW METER
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. DISCONNECT AIR FLOW METER CONNECTOR
(a) Disconnect the air flow meter connector.
(b) Disconnect the wire clamp from the clamp bracket onthe air flow meter.
3. REMOVE AIR CLEANER CASE AND AIR FLOW METER ASSEMBLY
(a) Loosen the hose clamp.
(b) Remove the four mounting bolts.
(c) Disconnect the air cleaner hose from the air flow meter.
(d) Disconnect the air duct from the air cleaner case, andremove the air cleaner case and air flow meter
assembly.
FI±64
EFI SYSTEM
± Air Induction System (Air Flow Meter)
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REMOVAL OF THROTTLE BODY
(See Components on page FI±69)
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
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 (See page CO±6)
3. REMOVE THROTTLE BODY COVER (a) Remove the mounting cap nut.
(b) Loosen the two bolts, and remove the throttle bodycover.
4. DISCONNECT CONTROL CABLES FROM THROTTLE BODY
Disconnect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System)
Cruise control actuator cable
5. REMOVE INTAKE AIR CONNECTOR (a) Disconnect the following hoses:(1) Air hose from ISC valve
(2) Air hose (from PS air control valve) from intake air connector
(b) Remove the bolt holding the intake air connector to the cylinder head cover.
(c) Loosen the two hose clamps.
(d) Disconnect the intake air connector from the throttle body and air cleaner hose, and remove the intake air
connector.
FI±70
EFI SYSTEM
± Air Induction System (Throttle Body)
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11. RECONNECT DRIVER BELTInstall the drive belt by turning the drive belt tensioner clock-
wise.
12. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
13. REFILL WITH ENGINE COOLANT
Knock Sensors
INSPECTION OF KNOCK SENSORS
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
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.
±
EFI SYSTEM Electronic Control System (Water Temperature Sensor)FI±69
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EGR Gas Temperature Sensor (USA Spec. only)
INSPECTION OF EGR GAS
TEMPERATURE SENSOR
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
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. REMOVE EGR GAS TEMPERATURE SENSOR (a) D i s c onnect the EGR gas temperature sensor
connector.
(b) Remove the EGR gas temperature sensor and gasket.
3. INSPECT EGR GAS TEMPERATURE SENSOR Using an ohmmeter, measure the resistance between the ter-
minals.
Resistance: 69±89 k
at 50 5C (112 5F)
12±15 k
at 100 5C (212 5F)
2±4 k
at 150 5C (302 5F)
If the resistance is not as specified, replace the sensor.
±
EFI SYSTEM Electronic Control System (EGR Gas Temperature
Sensor (USA Spec. only)FI±71
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INSPECTION OF SUB±OXYGEN SENSOR
1. INSPECT SUB±OXYGEN SENSOR(a) Cancel diagnostic code. (See TR section)
(b) A llo w th e en g in e to wa rm up to no rma l op e ra tin gtemperature.
(c) Drive for 5 minutes or more between 80km/h (50 mph) and 100 km/h (62 mph) in ºDº range.
(d) Following the conditions in step (c), press fully on the
accelerator pedal for 2 seconds or more.
HINT: Do not exceed 100 km/h (62 mph), or diagnostic code
will be cancelled.
(e) Stop the vehicle, and turn the ignition switch to OFF.
(f) Carry out steps (b), (c) and (d) again to test acceleration.
If code No. 27 reappears again, check the sub±oxygen sen-
sor circuit. If the circuit is normal, replace the sub±oxygen
sensor.
2. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
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.
3. REMOVE TRANSMISSION SHIFT LEVER KNOB (A/T)
(a) Push down the lever cover.
(b) Remove the two screws and shift lever knob.
(c) Remove the lever cover.
±
EFI SYSTEMFI±77Electronic Control System (Sub±Oxygen Sensor (USA Spec. only))
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INSPECTION OF FUEL PUMP ECU
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
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. REMOVE SEAT CUSHION AND BACK
3. REMOVE QUARTER TRIM (a) Disconnect the rear side of the scuff plate by pulling it.
(b) Remove clip A.
(c) Remove the belt hole cover by pulling it.
(d) Remove clip B.
(e) Remove the quarter trim by pulling it.
4. DISCONNECT FUEL PUMP ECU CONNECTOR
FI±82
±
EFI SYSTEM Electronic Control System (Fuel pump ECU)
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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 COLD START
INJECTOR TIME SWITCH
1. REMOVE LOWER HIGH±TENSION CORD COVER(See steps 1, 2 and 5 to 12 on pages FI±27 to 29)
2. REMOVE RH IGNITION COIL (a) Disconnect the ignition coil connector.
(b) Remove the two bolts, and disconnect the ignition coil.
(c) Disconnect the cam position sensor connector from the
ignition coil bracket, and remove the ignition coil.
3. REMOVE COLD START INJECTOR TIME SWITCH (a) Disconnect the injector time switch connector.
(b) Remove the injector time switch and gasket.
4. INSPECT COLD START INJECTOR TIME SWITCH Using an ohmmeter, measure the resistance between each
terminal.
Resistance:
STA±STJ 25±45
below 15 °C (59 °F)
65±85
above 30 °C (86 °F)
STA±Ground 25±85

If the resistance is not as specified, replace the switch.
5. REINSTALL COLD START INJECTOR TIME SWITCH (a) Install a new gasket to the injector time switch.
(b) Install the injector time switch.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
(c) Connect the injector time switch connector.
6. REINSTALL RH IGNITION COIL (a) Install the ignition coil with the two bolts.
FI±88
EFI SYSTEM
± Electronic Control System (Cold Start Injector Time Switch)
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(b) Install the cam position sensor connector to the ignitioncoil bracket.
(c) Connect the ignition coil connector.
7. REINSTALL LOWER HIGH±TENSION CORD COVER (See steps 1 to 13 and 16 to 18 on pages FI±39 to 41)FI±89
EFI SYSTEM
± Electronic Control System (Cold Start Injector Time Switch)
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INSPECTION OF VSV FOR FUEL
PRESSURE CONTROL
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. REMOVE VSV (a) Disconnect the VSV connector.
(b) Disconnect the following hoses from VSV:(1) Vacuum hose (from fuel pressure regulator)
(2) Vacuum hose (from air intake chamber)
(c) (Exc. USA Spec.) Remove the bolt holding the water by±pass pipe to the
VSV.
(d) Remove the bolt and VSV.
FI±92
EFI SYSTEM
± Electronic Control System (VSV for Fuel Pressure Control)
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