1991 LEXUS SC400 Service Repair Manual

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Page 2633 of 4087

LEXUS SC400 1991 Service Repair Manual
FAIL±SAFE CHART
If any of the following codes is recorded, the ECU enters fail±
safe mode.
Code No.Fail±Safe OperationFail±Safe Deactivation Conditions
14Fuel cut1 IGF1 detected in consecutive 8

FAIL±SAFE CHART
If any of the following codes is recorded, the ECU enters fail±
safe mode.
Code No.Fail±Safe OperationFail±Safe Deactivation Conditions
14Fuel cut1 IGF1 detected in consecutive 8 ignitions.
15Fuel cut1 IGF2 detected in consecutive 8 ignitions.
16Torque control prohibited.Returned to normal condition.
22THW is fixed at 805C (176 5F).Returned to normal condition.
24THA is fixed at 20 5C (68 5F).Returned to normal condition.
31
Ignition timing controlled between 10 5 ~ 30 5
BTDC,
Injection time controlled between 3 msec. ~ 30 m
sec., in relation to:
w Engine rpm
w Throttle angle
w ISC step value
KS input 15 times/sec. or more.
35Atmospheric pressure is fixed at 760 mmHg.Returned to normal condition.
The following 1 or 2 must be repeated at least 2
times consecutively.
41VTA1 is fixed at 051 When IDL is ON41VTA1 is fixed at 051 When IDL is ON
0.25 V VTA1 0.95 V
2 When IDL is OFF2 When IDL is OFF
0.25 V VTA1 4.9 V
The following 1 or 2 must be repeated at least 2
times consecutively.
47Value of VTA1 is used1 When IDL2 is ON47Value of VTA1 is used.1 When IDL2 is ON
0.25 V VTA2 0.95 V
2 When IDL2 is OFF2 When IDL2 is OFF
0.25 V VTA2 4.9 V
52Max. timeing retardation.IG switch OFF.
53Max. timeing retardation.Returned to normal condition.
55Max. timeing retardation.IG switch OFF.
Back±Up Function
If there is trouble with the program in the ECU and the ignition signals\
(IGT) are not output, the ECU controls
fuel injection and ignition timing at predetermined levels as a back±up f\
unction to make it possible to continue
to operate the vehicle.
Furthermore, the injection duration is calculated from the satrting sign\
al (STA) and the throttle position signal
(IDL). Also, the ignition timing is fixed at the initial ignition timing, 5 5 BTDC, without relation to the engine speed.
HINT: If the engine is controlled by the back±up function, the CHECK ENGIN\
E light lights up to warn the driver
of the malfunction but the diagnostic code is not output. TR±22
±
ENGINE TROUBLESHOOTING Fail±Safe Chart
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Page 2634 of 4087

LEXUS SC400 1991 Service Repair Manual
CHECK FOR MOMENTARY
INTERRUPTION
As described in the preceding paragraph, abnormality detection
ability in the test mode is increased compared to that in the normal
mode, so that when momentary inter

Page 2635 of 4087

$LEXUS SC400 1991 Service Repair Manual YESNO NOYES YES NO OKNG BASIC INSPECTION When the normal code is displayed in the diagnostic code check, troubleshoot\ ing should be performed in the order for all possible circuits to be considered$

Page 2636 of 4087

LEXUS SC400 1991 Service Repair Manual
OKNG
OKNG
5Check idle speed.
C
OK
P(1) Warm up engine at normal operating temperature.
(2) Switched off all accessories.
(3) Switched off air conditioner.
(4) Shift transmission into ªNº range.
(5)

Page 2637 of 4087

LEXUS SC400 1991 Service Repair Manual
OKNG
OKNG
7Check fuel pressure.
C
P(1) Be sure that fuel is enough in tank.
(2) Turn ignition switch on.
(3) Using SST, connect terminals FP and + B of checkconnector.
SST 09843±18020
Check that pul

Page 2638 of 4087

LEXUS SC400 1991 Service Repair Manual
PARTS LOCATION
±
ENGINE TROUBLESHOOTING Parts locationTR±27
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Page 2639 of 4087

LEXUS SC400 1991 Service Repair Manual
WIRING DIAGRAM
TR±28±
ENGINE TROUBLESHOOTING Wiring Diagram
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Page 2640 of 4087

LEXUS SC400 1991 Service Repair Manual
±
ENGINE TROUBLESHOOTING Wiring DiagramTR±29
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