1991 LEXUS SC400 check engine

D. Check and adjust DP setting speed(a) Maintain the engine at 2,500 rpm.
(b) Plug the VTV hole with your finger.
(c) Release the throttle valve.
(d) Check that the DP is set.
DP setting speed: 1,500 rpm
(e) Adjust the DP setting speed by turning the DP adjusting
screw.
(f) Repeat steps from (a) to (c), and recheck the DP setting
speed.
E. Reinstall separator, filter and cap to DP HINT: Install the filter with the coarser surface facing the at-
mospheric side (outward).
F. Check VTV operation (a) Maintain the engine at 2,500 rpm.
(b) Release the throttle valve, and check that the enginereturns to idle in a few seconds.
FI±68
EFI SYSTEM
± Air Induction System (Throttle Body)
WhereEverybodyKnowsYourName

Main Oxygen Sensors
INSPECTION OF MAIN OXYGEN
SENSORS
1. WARM UP ENGINEAllow 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 (ºDIAGNOSISº) 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
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Replace the ECU
Zero againAfter replacing
the oxygen sensor
Normal
8 times
or moreZero
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 26Malfunction 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)
WhereEverybodyKnowsYourName

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 kW 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
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Idle Speed Control (ISC) Valve
ON±VEHICLE INSPECTION
INSPECT ISC VALVE FOR OPERATING SOUNDCheck that there is a clicking sound immediately after stop-
ping the engine.
If the rpm operation is not as specified, check the ISC valve,
wiring and ECU.
FI±80
± Air Induction System (Idle Speed Control (ISC\
) Valve)EFI SYSTEM
WhereEverybodyKnowsYourName

EFI Main Relay
INSPECTION OF EFI MAIN RELAY
1. REMOVE EFI MAIN RELAY FROM RELAY BOX IN ENGINE
COMPARTMENT
2. INSPECT EFI MAIN RELAY
A. Inspect relay continuity (a) Using an ohmmeter, check that there is continuity
between terminals 1 and 3.
(b) Check that there is no continuity between terminals 2 and 4.
If continuity is not as specified, replace the relay.
B. Inspect relay operation (a) Apply battery voltage across terminals 1 and 3.
(b) Using an ohmmeter, check that there is continuity
between terminals 2 and 4.
If operation is not as specified, replace the relay.
3. REINSTALL EFI MAIN RELAY FI±85
± Electronic Control System (EFI Main Relay\
)EFI SYSTEM
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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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(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)
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