Lexus SC300 / Lexus SC400. Manual — part 481
Main Oxygen Sensors
INSPECTION OF MAIN OXYGEN
SENSORS
1.
WARM UP ENGINE
Allow the engine to warm up to normal operating tempera-
ture.
2.
INSPECT FEEDBACK VOLTAGE
Connect the positive (+) probe of a voltmeter to terminal VF1
(for No.1) or VF2 (for No.2) of the check (”DIAGNOSIS”) con-
nector, and negative (–) probe to terminal E1. Perform 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
–
EFI SYSTEM
Electronic Control System (Main Oxygen Sensors)
FI–73
Replace the ECU
Zero again
After replacing
the oxygen sensor
Normal
8 times
or more
Zero
Check the number of times the voltmeter needle fluctuates in 10 seconds
Zero
8 times or more
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
Warm up the engine 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.
Less than 8 times
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Measure voltage between terminals VF1 (VF2) and E1.
Less than 8 times
More than 0V
0V
Normal code, code
Nos. 21, 25, and 26
Malfunction code(s)
(Ex. code Nos. 21, 25 and 26
Read and record diagnostic codes. (See TR section)
Repair the relevant diagnostic code
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Read and record diagnostic codes. (See TR section)
Malfunction code(s)
(Ex. code Nos. 21, 25 and 26
Normal code, code
Nos. 21, 25, and 26
Repair the relevant diagnostic code
FI–74
–
EFI SYSTEM
Electronic Control System (Main Oxygen Sensors)
Measure voltage between terminals VF1 (VF2) and E1.
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Measure voltage between terminals VF1 (VF2) and E1.
Disconnect the PCV hose.
0V
5V
More than 0V
Repair (Over rich)
Disconnect the water temp. sensor connector and connect
resistor with a resistance of 4 – 8 k
Ω
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.
Replace the oxygen sensor.
Repair (Over lean)
5V
0V
–
EFI SYSTEM
Electronic Control System (Main Oxygen Sensors)
FI–75
Sub–Oxygen Sensor (USA Spec. only)
COMPONENTS FOR REMOVAL AND
INSTALLATION
FI–76
–
EFI SYSTEM
Electronic Control System (Sub–Oxygen Sensor (USA Spec. only))
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