ECU LEXUS SC400 1991 Service Repair Manual

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
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Fuel Pump ECU
COMPONENTS FOR REMOVAL AND
INSTALLATION
±
EFI SYSTEM Electronic Control System (Fuel pump ECU)FI±81
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INSPECTION OF FUEL PUMP ECU
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
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.
2. REMOVE SEAT CUSHION AND BACK
3. REMOVE QUARTER TRIM (a) Disconnect the rear side of the scuff plate by pulling it.
(b) Remove clip A.
(c) Remove the belt hole cover by pulling it.
(d) Remove clip B.
(e) Remove the quarter trim by pulling it.
4. DISCONNECT FUEL PUMP ECU CONNECTOR
FI±82
±
EFI SYSTEM Electronic Control System (Fuel pump ECU)
WhereEverybodyKnowsYourName

5. INSPECT FUEL PUMP ECU(a) Connect the cable to the negative (±) terminal of thebattery.
(b) Check the connector on the wiring harness side as shown in the chart.
Check forTester connectionConditionSpecified value
ContinuityE±Ground±Continuity
ContinuityDI±Ground±Continuity
VoltageFP GroundSudden racing12±14 VVoltageFP±GroundIdling8±10 V
Voltage+B±GroundIG SW ON8±16 V
VoltageFPC±Ground
Sudden racing
(6,000 rpm or more)4±6 VVoltageFPC Ground
Idling2.5 V
If circuit is as specified, replace the fuel pump ECU.
(c) Disconnect the cable from the negative (±) terminal of the battery.
6. RECONNECT FUEL PUMP ECU CONNECTOR
7. INSTALL QUARTER TRIM (a) Attach the upper side of the quarter trim to the quarterpanel.
(b) Install the quarter trim with the four clips.
±
EFI SYSTEM Electronic Control System (Fuel pump ECU)FI±83
WhereEverybodyKnowsYourName

(c) Install the belt hole cover with the two clips.
(d) Install the rear side of the scuff.
8. REINSTALL SEAT BACK AND CUSHION
9. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
FI±84
±
EFI SYSTEM Electronic Control System (Fuel pump ECU)
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)
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Fuel pump ECU
COMPONENTS FOR REMOVAL AND
INSTALLATION
FI±122 ± Electronic Contro\
l System (Fuel Pump ECU)EFI SYSTEM
WhereEverybodyKnowsYourName

INSPECTION OF FUEL PUMP ECU
1. 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.
2. REMOVE SEAT CUSHION AND BACK
3. REMOVE QUARTER TRIM
(a) Disconnect the rear side of the scuff plate by pulling it.
(b) Remove clip A.
(c) Remove the belt hole cover by pulling it.
(d) Remove clip B.
(e) Remove the quarter trim by pulling it.
4. DISCONNECT FUEL PUMP ECU CONNECTOR FI±123
EFI SYSTEM
± Electronic Control System (Fuel Pump ECU)
WhereEverybodyKnowsYourName

5. INSPECT FUEL PUMP ECU(a) Connect the cable to the negative (±) terminal of thebattery.
(b) Check the connector on the wiring harness side as shown in the chart.
Check forTester connectionConditionSpecified value
ContinuityE ± Ground±Continuity
ContinuityDI ± Ground±Continuity
VoltageFP GroundSudden racing12 ± 14 VVoltageFP ± GroundIdling8 ± 10 V
Voltage+ B ± GroundIG SW ON10 ± 14 V
VoltageFPC ± Ground
Sudden racing
(1,600 rpm or more)4 ± 6 VVoltageFPC Ground
Idling2.5 V
If circuit is as specified, replace the fuel pump ECU.
(c) Disconnect the cable from the negative (±) terminal of the battery.
6. RECONNECT FUEL PUMP ECU CONNECTOR
7. INSTALL QUARTER TRIM (a) Attach the upper side of the quarter trim to the quarterpanel.
(b) Install the quarter trim with the four clips.
FI±124
EFI SYSTEM
± Electronic Control System (Fuel Pump ECU)
WhereEverybodyKnowsYourName

(c) Install the belt hole cover with the two clips.
(d) Install the rear side of the scuff.
8. REINSTALL SEAT BACK AND CUSHION
9. RECONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY FI±125
EFI SYSTEM
± Electronic Control System (Fuel Pump ECU)
WhereEverybodyKnowsYourName