ECU LEXUS SC400 1991 Service Repair Manual

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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

AIR CONDITIONING EVAPORATOR ± AC001±97 September 12, 1997
ES 3003. Reinstallation of parts.
('92±'96)
(Continued) (a) Insert the filter (up side) into the
heater unit following the numbered
steps shown in the illustration.
(b) Insert the filter (down side) into the heater unit.
(c) Reinstall the plate on the side of the heater unit using steps and
,
indicated with red arrows to show
direction, in the illustration.
CAUTION:
Confirm that the plate is secure.
(d) Restore the carpet to its original position taking care not to bend
the cable.
Page 4 of 11
WhereEverybodyKnowsYourName

AIR CONDITIONING EVAPORATOR ODOR ± AC001±97 September 12, 1997
GS 3003. Reinstallation of parts.
(Continued) (a) Insert the (2) filters into the cooling
unit as shown in the illustration.
NOTE:
Insert a clean air filter with it's knob
facing downwards, then slide it forward
and install the second filter in the same
manner.
(b) Assemble the rubber insulator on the plate.
CAUTION:
To prevent the cooling unit from leaking
water, pull the three rubber projections
from the other side of the plate to make
sure that the rubber insulator seals
properly against the plate.
(c) Install the plate on the cooling unit and secure with the (2) wing nuts.
CAUTION:
To prevent water leaks, verify that the
cooling unit and plate are fully secure
before tightening the wing nuts.
NOTE:
Before installing the plate on the cooling
unit, coat the rubber insulator with water
for easier assembly.
(d) Reinstall the lamp.
(e) Reassemble the Undercover.
Page 6 of 11
WhereEverybodyKnowsYourName

AIR CONDITIONING EVAPORATOR ODOR ± AC001±97 September 12, 1997
LS 4003. Reinstallation of parts.
('93±'94)
(Continued) (a) Insert the (2) filters into the cooling
unit as shown in the illustration.
NOTE:
Insert a clean air filter with it's knob
facing downwards, then slide it forward
and install the second filter in the same
manner.
(b) Assemble the rubber insulator on the plate.
CAUTION:
To prevent the cooling unit from leaking
water, pull the three rubber projections
from the other side of the plate to make
sure that the rubber insulator seals
properly against the plate.
(c) Install the plate on the cooling unit and secure with the (2) wing nuts.
CAUTION:
To prevent water leaks, verify that the
cooling unit and plate are fully secure
before tightening the wing nuts.
NOTE:
Before installing the plate on the
cooling unit, coat the rubber insulator
with water for easier assembly.
(d) Reinstall the lamp.
(e) Reassemble the Undercover.
Page 8 of 11
WhereEverybodyKnowsYourName

AIR CONDITIONING EVAPORATOR ODOR ± AC001±97 September 12, 1997
SC 3003. Reinstallation of parts.
SC 400
(Continued) (a) Insert the (2) filters into the cooling
unit as shown in the illustration.
NOTE:
Insert a clean air filter with it's knob
facing downwards, then slide it forward
and install the second filter in the same
manner.
(b) Assemble the rubber insulator on the plate.
CAUTION:
To prevent the cooling unit from leaking
water, pull the three rubber projections
from the other side of the plate to make
sure that the rubber insulator seals
properly against the plate.
(c) Install the plate on the cooling unit and secure with the (2) wing nuts.
CAUTION:
To prevent water leaks, verify that the
cooling unit and plate are fully secure
before tightening the wing nuts.
NOTE:
Before installing the plate on the
cooling unit, coat the rubber insulator
with water for easier assembly.
(d) Reassemble the Undercover.
Page 10 of 11
WhereEverybodyKnowsYourName