LEXUS SC400 1991 Service Repair Manual

PARTS LOCATION
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ENGINE TROUBLESHOOTING Parts locationTR±27
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WIRING DIAGRAM
TR±28±
ENGINE TROUBLESHOOTING Wiring Diagram
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ENGINE TROUBLESHOOTING Wiring DiagramTR±29
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TERMINALS OF ECU
Connectors of the engine & ECT ECU are water±proof and are the
bolt type.
For water proof type connectors, in order to measure the voltage
of ECU terminals and the resistance of connected parts, connect
the inspection sub wire harness between the ECU and vehicle
wire harness, then perform the inspection. The inspection method
of inserting a tester probe from the other side of connector notice-
ably reduces the water±proof ability.
Disconnect the connector by fully loosening the bolt.
PREPARATION
1. Turn the ignition switch to LOCK position.
2. Turn up the passenger side floor mat.
3. Remove the ECU protector.
4. Disconnect the connector from the ECU. After completely loosening the bolt, the two parts of the con-
nector can be separated.
NOTICE:
w Do not pully the wire harness when disconnecting the
connector.
w When disconnecting the connector, the ECU's backup
power source is cut off, so the malfunction codes, etc.
recorded in the ECU memory are cancelled.
w Never insert a tester probe or male terminal used for
inspection purposes into the female terminal of the
vehicle wire harness. Otherwise, the female terminal may
be widened, which can result in faulty connection.
5. Connect the Check Harness A between ECU and connector
of vehicle wire harness.
SST 09990±01000
HINT: The arrangement of the check connector terminals are
the same as those of the ECU.
See page TR±31
6. Disconnect the Check Harness A.
7. Reconnect the connector to the ECU.
(a) Match the male connector correctly with the femaleconnector, then press them together.
(b) Tighten the bolt Make sure the connector is completely connected, by
tightening the bolt until there is a clearance of less than
1 mm (0.04 in.) between bottom of the male connector
and end of the female connector.
8. Install the ECU protector and floor mat.
TR±30
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ENGINE TROUBLESHOOTING Terminals of ECU
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TERMINALS OF ECU
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ENGINE TROUBLESHOOTING Terminals of ECUTR±31
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TERMINALS OF ECU (Cont'd)
TR±32±
ENGINE TROUBLESHOOTING Terminals of ECU
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PARTS LOCATION
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ENGINE TROUBLESHOOTING Parts locationTR±31
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WIRING DIAGRAM
TR±32±
ENGINE TROUBLESHOOTING Wiring Diagram
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ENGINE TROUBLESHOOTING Wiring DiagramTR±33
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STANDARD VALUE OF ECU TERMINALS
Symbols (Terminals No.)STD Voltage (V)Condition
BATT (A33) ± E1 (B69)10 ~ 14Always
IGSW (A1)IGSW (A1)
+ B (A31)± E1 (B69) 10 ~ 14IG switch ON+ B (A31)
+ B1 (A32)
E1 (B69)10 14IG switch ON
VC (B41)±E2 (B65)4.0 ~ 6.0IG switch ON
Below 1 0IG switch ON
IDL1 (B64)E2 (B65)
Below 1.0IG switch ON
Main or sub throttle valve fully closed.IDL1 (B64)
IDL2 (B63)± E2 (B65)
10 14IG switch ON()10 ~ 14IG switch ON
Main or sub throttle valve fully open.
01 10IG switch ON
VTA1 (B43)E2 (B65)
0.1 ~ 1.0IG switch ON
Throttle valve fully closed.VTA1 (B43)
VTA2 (B42)± E2 (B65)
30 60IG switch ON()3.0 ~ 6.0IG switch ON
Throttle valve fully open.
KS (B66) ± E1 (B69)Pulse generation(0 and 4 ~ 6)Idling
THA (B45) ± E2 (B65)1.0 ~ 3.0Idling, Intake air temp. 20 5C (68 5F).
THW (B44) ± E2 (B65)0.1 ~ 1.0Idling, Water temp. 80 5C (176 5F).
STA (B77) ± E1 (B69)6.0 or moreCranking
#10 (B20), #20 (B19)E01 (B80)10 ~ 14IG switch ON#10 (B20), #20 (B19)
#30 (B18), #40 (B17)± E01 (B80)Pulse generationIdling
IGT1 (B57), IGT2 (B56) ± E1 (B69)Pulse generation
(0 and 4 ~ 6)Idling
Below 1.0IG switch ON
IGF1 (B58), IGF2 (B59) ± E1 (B69)Pulse generation(0 and 4 ~ 6)Idling
G1 (B26), G2 (B25) ± G1
(B6)Pulse generation
(±1.0 ~ +1.0 or higher)Idling
NE (B27) ± NE
(B7)Pulse generation
(±0.8 ~ +0.8 or higher)Idling
MREL (A24) ± E1 (B69)10 ~ 14IG switch ON
4.2 ~ 6.0Cranking, Sudden racing (6,000 rpm)
FPC (A22) ± E1 (B69)Pulse generation (0 and 4 ~ 6)Idling
DI (A21) ± E1 (B69)7.5 or moreIdling
FPU (B73) E1 (B69)10 ~ 14IG switch ONFPU (B73) ± E1 (B69)Below 2.0Restarting high temp.
PAG (B74) ± E1 (B69)10 ~ 14Idling
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ENGINE TROUBLESHOOTING Standard Value of ECU TerminalsTR±33
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