Lexus SC300 / Lexus SC400. Manual — part 492

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)

Main Oxygen Sensors

INSPECTION OF MAIN OXYGEN
SENSORS

1.

WARM UP ENGINE
Allow 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 (”DIAGNO-
SIS”) 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

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)

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 V

5 V

More than 0 V

FI–115

EFI SYSTEM – Electronic Control System (Main Oxygen Sensors)