LEXUS SC400 1991 Service Repair Manual

Check voltage of ECU power source.
Check continuity between terminals E1 and
body ground.
Check voltage of terminal IGSW.
Check IGN fuse.
Check ignition switch.
Check for open in harness and connector
between battery and ECU.
Check voltage of terminal M±REL.
Check EFI fuse.
Check EFI main relay.Check for open and short in harness and
connector between terminal M±REL and
body ground.
Check and repair harness or connector
between EFI fuse and battery.
Repair or replace harness or
connector.
Replace EFI main relay.
Check for short in all the harness
and components connected to the
EFI fuse.
Check and replace ECU.
Replace ignition switch.
Check for short in all the harness and
components connected to IGN fuse.
Repair or replace harness or
connector.
Proceed to next circuit inspection
shown on matrix cart (See page
TR±39
).
DIAGNOSTIC CHART
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±121
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NGOK
OKNG
NGOK
INSPECTION PROCEDURE
1Check voltage between terminals +B, +B1 and E1 of engine (& ECT) ECU connec\
tor.
C
OK
P1. Connect the Check Harness A. (See page TR±34)
2. Turn ignition switch on.
Measure voltage between terminals +B, +B1 and E1
of engine (& ECT) ECU connector.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix chart
(See page TR±39).
2Check for open in harness and connector between terminal E1 of engine (\
& ECT) ECU and
body ground. (See page IN±27).
Repair or replace harness or connector.
3Check voltage between terminal IGSW of engine (& ECT) ECU connector an\
d body ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal IGSW of engine
(& ECT) ECU connector and body ground.
Voltage: 10 ± 14 V
Go to step
.
TR±122
±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
4Check IGN fuse.
C
OK
PRemove IGN fuse from J/B No. 1.
Check continuity of IGN fuse.
Continuity
Check for short in all the harness and components con-
nected to IGN fuse (See attached wiring diagram).
5Check ignition switch.
C
OK
PRemove under cover and finish panel.
Check continuity between terminals.
Replace ignition switch.
Check and repair harness and connector between
battery and ignition switch, ignition switch and en-
gine (& ECT) ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±123
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OKNG
OKNG
6Check voltage between terminal M±REL of engine (& ECT) ECU connector and\
body ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal M±REL of engine
(& ECT) ECU connector and body ground.
Voltage: 10 ± 14 V
Check and replace engine (& ECT) ECU.
7Check EFI fuse.
C
OK
PRemove EFI fuse from R/B No. 2.
Check continuity of EFI fuse.
Continuity
Check for short in all the harness and components
connected to EFI fuse (See attached wiring diagram).
TR±124
±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
8Check EFI main relay.
C
OK
P
OK
C
Remove EFI main relay.
Check continuity between terminals of EFI main relay
shown below.
1. Apply battery positive voltage between terminals 1and 3.
2. Check continuity between terminals 2 and 4.
Replace EFI main relay.
9Check for open and short in harness and connector between terminal M±REL of\
engine (& ECT)
ECU and body ground (See page IN±27).
Repair or replace harness or connector.
Check and repair harness or connector between
EFI fuse and battery.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±125
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Neutral Start Switch Circuit
CIRCUIT DESCRIPTION
The neutral start switch goes on when the shift lever is in the N or P shif\
t position. When it goes on the terminal
NSW of the ECU is grounded to body ground via the starter relay and theft deterrent ECU\
, thus the terminal
NSW voltage becomes 0V. When the shift lever is in the D, 2, L or R position, the neutral start\
switch goes off,
so the voltage of ECU terminal NSW becomes battery voltage, the voltage of the ECU internal power source.
If the shift lever is moved from the N range to the D range, this signal\
is used for air±fuel ratio correction and
for idle speed control (estimated control), etc.
When the neutral start switch is off, code º51º is output in the test mode diagnosis. (This is not a\
bnormal.)
DIAGNOSTIC CHARTDIAGNOSTIC CHART
HINT: This diagnosis chart is based on premise that the engine is cranked norm\
ally. If the engine is notcranked, proceed to the matrix chart of problem symptoms on page TR±35.
Check output condition of diag. code 51.
Proceed to next circuit inspection shown
on matrix chart (See page TR±35).
Check for open in harness and connector
between neutral start switch and ECU.
Repair or replace harness or connector.
Check and replace ECU.
Check and replace ECU.
Replace neutral start switch.Check neutral start switch (See page
AT±100 ).
TR±122
±
ENGINE TROUBLESHOOTING Circuit Inspection
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OK
NG
Type I
NG
Type II
NG
OK
OKNG
INSPECTION PROCEDURE
1Check output condition of diag. code 51.
C
P(2) Connect terminals TE2 and E1 of TDCL.
(2) Turn ignition switch on.
(2) Crank the engine.
(2) Connect terminal TE1 and E1 of TDCL.
Check if diagnostic code ª51º is output when then shift
level is in the P and D shift positions.
Result:
Go to step 2.
Go to step 3.
Proceed to next circuit inspection shown on ma-
trix chart (See page TR±35).
2
Check for open in harness and connector between engine & ECT ECU and neutral \
start switch
(See page IN±27).
Check and replace engine & ECT ECU.
Repair or replace harness or connector.
3Check neutral start switch (See page AT±100).
Replace neutral start switch.
Check and replace engine & ECT ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±123
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VALVE CLEARANCE ADJUSTING TOOL SETPage 1 of 1
The Valve Lifter Press has undergone two modifications that will improve service procedures
on UZ and VZ series engines.
1. Due to space limitations on these engines, the thickness of the valve li\
fter press jaws and its connecting rivet have been reduced. This reduction will allow pr\
oper
compression of the cam follower and spring without the tool slipping out\
of position.
2. The front jaw angle on the valve lifter press has also been modified. Th\
is change will allow easier installation of the tool between the camshaft and the follo\
wer, and also
provide improved leverage for the compression of the cam follower and sp\
ring.
The updated tool set, Part Number 09248±55020, supersedes your previous \
09248±55010
tool set. This new tool set will service all current Lexus engines.
SST'S/SSI'S
001
OCTOBER 11, 1991
ALL MODELS
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A/C COMPRESSOR OIL APPLICATIONSPage 1 of 1
Care must be taken to use only refrigerant oil which is compatible to the vehicle's system.
Following are A/C oil application charts for both R±12 and HFC±134\
a systems:
R±12 SYSTEMS
MODEL OIL TYPE PART NUMBER QUANTITY
All Models ND±Oil 6 P/N (88899±28040) 60 cc (or Equivalent) P/N (07117±68040) 500 cc
HFC±134A SYSTEMS MODEL OIL TYPE PART NUMBER QUANTITY
All Models ND±Oil 8 P/N (08885±09109) 40 cc P/N (08885±09107) 250 cc
HEATING & AIR CONDITIONING
AC93±004
OCTOBER 22, 1993
ALL MODELS
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DATE:JULY 19, 1996
Title1992 - 1995 SC 300/400 A/C CONTROL ASSEMBLY SERVICE PARTSPage 1 of 6
To allow repairs to the A/C Control Assembly, service parts are now available. The following
information on parts and troubleshooting will aid you in addressing comp\
laints with the LCD
display, night illumination or switch indicators.
PREVIOUSLY AVAILABLE PARTS
:
CURRENTLY AVAILABLE PARTS
:
* Face Plate is not available as a separate part.
REF: HEATING & AIR CONDITIONING
NO:AC004-96
MODEL:SC 300/400
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