oxygen sensor LEXUS SC400 1991 Service Owner's Guide

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))
WhereEverybodyKnowsYourName

4. (A/T)
REMOVE CUP HOLDERUsing a screwdriver, pry out the rear side of the cup holder.
Remove the cup holder.
5. REMOVE UPPER REAR CONSOLE PANEL Using a screwdriver, pry out the console panel.
6. (A/T)
REMOVE UPPER CONSOLE PANEL (a) Remove the six mounting screws.
(b) Using a screwdriver, pry out the console panel.
7. DISCONNECT SUB±OXYGEN SENSOR CONNECTOR
8. INSPECT HEATER RESIST ANCE OF SUB±OXYGEN
SENSOR
Using an ohmmeter, measure the resistance between the ter-
minals +B and HT.
Resistance: 5.1±6.3
at 20 5C (68 5F)
FI±78±
EFI SYSTEM
Electronic Control System (Sub±Oxygen Sensor (USA Spec. only))
WhereEverybodyKnowsYourName

If the resistance is not as specified, replace the sensor as fol-
lows:
wDisconnect the grommet from the floor panel, and pull
out the wire of the sub±oxygen sensor from the floor
panel.
w Remove the two nuts, cover and sub±oxygen sensor
from the front exhaust pipe.
w Install a new gasket, a new sub±oxygen sensor and the
cover to the front exhaust pipe with the two nuts.
Torque: 18 N Vm (180 kgf Vcm, 13 ft Vlbf)
w Run the wire of the sub±oxygen sensor through the hole
in the floor panel.
9. RECONNECT SUB±OXYGEN SENSOR CONNECTOR
10. (A/T) REINSTALL UPPER REAR CONSOLE PANEL
(a) Fit the console panel to the console box with five clips.
(b) Install the console panel with the six screws.
11. REINSTALL UPPER CONSOLE PANEL Fit the console panel to the console box with the four clips.
12. (A/T) REINSTALL CUP HOLDER
Fit the cup holder to the console box.
±
EFI SYSTEMFI±79
Electronic Control System (Sub±Oxygen Sensor (USA Spec. only))
WhereEverybodyKnowsYourName

13. REINSTALL TRANSMISSION SHIFT LEVER KNOB(A/T)
(a) Slide the lever cover on the lever shaft.
(b) Install the shift lever knob with the two screws.
(c) Attach the l ever cover to the lower side of the lever knob.
14. RECONNECT CABLE TO NEGATIVE TERMINAL OF BAT-
TERY
FI±80
±
EFI SYSTEM
Electronic Control System (Sub±Oxygen Sensor (USA Spec. only))
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

Sub±Oxygen Sensors
COMPONENTS FOR REMOVAL AND
INSTALLATION
FI±117 ± Electronic Control System (Sub±Oxygen\
Sensors)EFI SYSTEM
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INSPECTION OF SUB±OXYGEN
SENSORS
1. INSPECT SUB±OXYGEN SENSORS(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: 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.
3. REMOVE TRANSMISSION SHIFT LEVER KNOB (a) Push down the lever cover.
(b) Remove the two screws and shift lever knob.
(c) Remove the lever cover.
FI±118
EFI SYSTEM
± Electronic Control System (Sub±Oxygen Sensors)
WhereEverybodyKnowsYourName