1991 LEXUS SC400 sensor

(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)
WhereEverybodyKnowsYourName

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)
WhereEverybodyKnowsYourName

(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)
WhereEverybodyKnowsYourName

19. INSTALL AIR INTAKE CHAMBER(See steps 2 to 18 on pages FI±35 to 41)
HINT: After the air intake chamber is installed, tighten the bolt
holding the EGR pipe to the RH cylinder head.
FI±112
EFI SYSTEM
± Electronic Control System (Knock Sensors)
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

Warm up the oxygen sensors with the engine at 2,500 rpm for
approx. 120 seconds.
Connect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Check the number of times the voltmeter needle fluctuates in 10 seconds.\
Warm up the oxygen sensors with the engine at 2,500 rpm.
for approx. 120 seconds. And maintain engine at 2,500 rpm.
Check the number of times the voltmeter needle
fluctuates in 10 seconds.
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Measure voltage between terminals VF1 (VF2) and E1.Replace the ECU.
Normal
Measure voltage between terminals VF1 (VF2) and E1.
Read and record diagnostic codes. (See TR Section)
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm. Repair the relevant diagnostic code. Repair the relevant diagnostic code.
Normal code, code Nos.
21, 25 and 26
Malfunction code(s)
(Ex. code Nos. 21, 25 and 26)
Malfunction code(s)
(Ex. code Nos. 21, 25 and 26)Normal code, code Nos.
21, 25 and 26
More than 0 V
0 V
Less than 8 times
Less than 8 times
8 times or more
8 times
or more
Zero
Zero
Zero again After replacing
the oxygen sensor
CONTINUED ON PAGE FI±115
FI±114
EFI SYSTEM
± Electronic Control System (Main Oxygen Sensors)
WhereEverybodyKnowsYourName

Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Repair (Over rich)
Replace the oxygen sensor.Repair (Over rich)
Measure voltage between terminals VF1 (VF2) and E1.
Disconnect the PCV hose.
Measure voltage between terminals VF1 (VF2) and E1.
Disconnect the water temp. sensor connector and connect
resistor with a resistance of 4 ± 8 k

or another coded water
temp. sensor.
Connect terminals TE1 and E1 of the check connector.
Warm up the oxygen sensors with the engine at 2,500 rpm for
approx. 120 seconds. and maintain engine at 2,500 rpm.
Measure voltage between terminals VF1 (VF2) and E1.
5 V
CONTINUED FROM PAGE FI±114
0 V
0 V
0 V5 V
More than 0 V
FI±115EFI SYSTEM ± Electronic Control System (Main Oxygen Sensors)
WhereEverybodyKnowsYourName

3. 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.
4. INSPECT HEATER RESIST ANCE OF MAIN OXYGEN
SENSORS
(a) Disconnect the oxygen sensor connectors.
(b) Using an ohmmeter, measure the resistance between the terminals +B and HT.
Resistance: 5.1±6.3
at 20 °C (68 °F)
If the resistance is not as specified, replace the sensor.
Torque: 44 N Vm (450 kgf Vcm, 33 ft Vlbf)
(c) Reconnect the oxygen sensor connectors.
5. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
FI±116
EFI SYSTEM
± Electronic Control System (Main Oxygen Sensors)
WhereEverybodyKnowsYourName