1991 LEXUS SC400 relay

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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Engine & ECT ECU
TERMINALS OF ENGINE & ECT ECU
TerminalNo.SymbolConnectionTerminalNo.SymbolConnection
E9 ± 1IGSWIgnition SwitchE9 ± 31+ BEFI Main Relay
2SPDNo. 1 Speed Sensor32+ B1EFI Main Relay
3KDKick±Down Switch33BATTBattery
4STPStop light Switch34A/CA/C Control Assembly
5±35±
6WªCHECKº Engine Warning Light36±
7RNeutral Start Switch37TRTRAC ECU
8±38NEOTRAC ECU
92Neutral Start Switch39VTO2TRAC ECU
10LNeutral Start Switch40VTO1TRAC ECU
11ADCC ECUE10 ± 1NCO T/M Input Speed Sensor
12OD1CC ECU2±
13±3SP2No. 2 Speed Sensor for ECT
14±4E11ECU Ground
15±5G2Cam position Sensor
16±6G1Cam position Sensor
17TTTDCL7NFEngine Speed Sensor
18PECT Pattern Select Switch8±
19TE2Check Connector9S2ECT Solenoid Value
20TE1Check Connector10S1ECT Solenoid Value
21D1Fuel Pump ECU11±
22FPCFuel Pump ECU12±
23ACMGA/C Magnet Clutch Relay13SLN
No.3 ECT Solenoid Valve
24M±RELEFI Main Relay14SLUNo.4 ECT Solenoid Valve
25±15±
26±16±
27±17#10No.3 and No.5 Injectors
28OD2O/D Main Relay18#20No.4 and No.6 Injectors
29±19#20No.2 and No.8 Injectors
30±20#40No.1 and No.7 Injectors
Engine & ECT ECU Terminals
FI±126 ± Electronic Control \
System (Engine & ECT ECU)EFI SYSTEM
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TERMINALS OF ENGINE & ECT ECU (Cont'd)
TerminalNo.SymbolConnectionTerminalNo.SymbolConnection
E10± 21NCOT/M Input Speed SensorE10 ± 51±
22±52HTL2LH Sub±Oxygen Sensor Heater
23SP2No.2 Speed Sensor for ECT53HTR2RH Sub±Oxygen Sensor Heater
24±54±
25G2LH (No.2) Cam Position Sensor55±
26G1RH (No.1) Cam Position Sensor56IGT2No.2 Igniter for RH Bank
27NEEngine Speed Sensor57IGT1No.1 Igniter for LH Bank
28VF2Check Connector58IGF1No.1 Igniter for LH Bank
29VF1Check Connector59IGF2No.2 Igniter for RH Bank
30±60±
31±61±
32ISC4ISC Valve62±
33ISC3ISC Valve63IDL2Sub±Throttle Position Sensor
34ISC2ISC Valve64IDL1Throttle Position Sensor
35ISC1ISC Valve65E2Sensor Ground
36* EGR4EGR Valve66KSAir Flow Meter
37* EGR3EGR Valve67OXR2
38* EGR2EGR Valve68OXL2LH Sub±Oxygen Sensor
39* EGR1EGR Valve69E1ECU Ground39* EGRVSV for EGR69E1ECU Ground
40±70±
41VCThrottle Position Sensor
Air Flow Meter71HTL1LH Main Oxygen Sensor
42VTA2Fuel Pump ECU72HTR1RH Main Oxygen Sensor
43VTA1A/C Magnet Clutch Relay73FPUVSV for Fuel Pressure Control
Value
44THWWater Temp. Sensor74* PA GVSV for EVAP
45THAIntake Air Temp. Sensor75±
46THGEGR Gas Temp. Sensor76NSWNeutral Start Switch
47OXR1RH Main Oxygen Sensor77STAStarter Relay
48OXL1LH Main Oxygen Sensor78STJCold Start Injector
49KNK2RH (No.2) Knock Sensor79E02Power Ground
50KNK1LH (No.1) Knock Sensor80E01Power Ground
Engine & ECT ECU Terminals
*USA spec. only
*  A/T only
FI±127EFI SYSTEM ± Electronic Control System (Engine & ECT ECU)
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IGNITION MAIN RELAY
INSPECTION OF IGNITION MAIN RELAY
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 IGNITION MAIN RELAY LOCATION: In the engine compartment relay box.
3. INSPECT IGNITION MAIN RELAY
A. Inspect relay continuity
(a) Using an ohmmeter, check that there is continuitybetween 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) Using an ohmmeter, check that there is continuity between terminals 1 and 2.
If operation is not as specified, replace the relay.
4. REINSTALL IGNITION MAIN RELAY
5. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
±
IGNITION SYSTEM Ignition Main RelayIG±31
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STARTER RELAY
INSPECTION OF STARTER RELAY
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
CAUTION: Work must be started after approx. 20 seconds or
longer from the time the ignition switch is turned to the
ºLOCKº position and the negative (±) terminal cable is dis-
connected from the battery.
2. REMOVE STATER RELAY LOCATION: In the engine compartment relay box.
3. INSPECT STARTER RELAY
A. Inspect relay continuity
(a) Using an ohmmeter, check that there is continuitybetween terminals 1 and 2.
(b) Check that there is no continuity between terminals 3 and 5.
If continuity is not as specified, replace the relay.
B. Inspect relay operation (a) Apply battery voltage across terminals 1 and 2.
(b) Using an ohmmeter, check that there is continuitybetween terminals 3 and 5.
If operation is not as specified, replace the relay.
4. REINSTALL STARTER RELAY
5. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
NEUTRAL START SWITCH
(See AT section)
THEFT DETERRENT SYSTEM
(See BE section)
±
STARTING SYSTEM Starter Relay, Neutral Start Switch, Theft Deterrent
SystemST±35
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Trouble Area
ºCHECKº
Engine Warning
Light *

Memory* See PageTrouble Area
Normal
ModeTest
Mode
MemorySee Page
w Open or short in air flow meter circuit.
w Air flow meter
w ECU
ONN.A.TR±88
wECUONONTR±92
wOpen or short in throttle position sensor circuit.
wThrottle position sensorONONTR±94Throttle osition sensor
w ECU
wNo. 1 speed sensor
w Combination meter
w Open or short in No. 1 speed sensor circuit.
w ECU
ONONTR±98
wOpen or short in starter signal circuit.
w Open or short in ignition switch or main relay circuit.
w ECU
N.A.OFFXTR±100
wOpen or short in sub±throttle position sensor circuit.
wSub±throttle position sensorOFFONTR±94Sub throttle osition sensor
wECU
wOpen or short in No. 1 knock sensor circuit.wOen or short in No. 1 knock sensor circuit.
w No. 1 knock sensor (looseness)
ONN.A.No. 1 knock sensor (looseness)
wECU

w ECUONN.A.XTR±102
w Open or short in No. 2 knock sensor circuit.w Oen or short in No. 2 knock sensor circuit.
w No. 2 knock sensor (looseness)
ONN.A. No. 2 knock sensor (looseness)
w ECU

*1, 2: See page TR±20.
±
ENGINE TROUBLESHOOTING Diagnostic Code ChartTR±19
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DIAGNOSTIC CHART
DIAGNOSTIC
CHART
Refer to inspection procedure in details.
HINT: If diag. code 14 is displayed, check No. 1 igniter circuit. If diag. code 15 is displayed, check No. 2 igniter circuit.
Check for spark.
Check for open and short in IGF signal circuit
between igniter and ECU.
Check voltage of terminal IGF.
Check and replace ECU.
Check voltage of terminal IGT.
Check voltage of igniter power source.
Check for open and short in primary coil circuit.
Check ignition coil.
Replace igniter.
Check and repair igniter power source circuit.
Check voltage of terminal IGT
(Disconnect igniter connector).
Check and repair igniter power source circuit. Repair or replace harness or
connector.
Replace igniter.
Repair or replace harness or
connector
Replace ignition relay.
Replace ignition relay.
Check for open and short in IGT signal circuit
between igniter and ECU.
Check and replace ECU. Repair or replace harness or
connectorReplace igniter.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±55
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