ECU LEXUS SC400 1991 Service Repair Manual

OKNG
OKNG
INSPECTION PROCEDURE
1Check key unlock warning switch.
C
OK
PDisconnect key unlock warning switch connector.
Check continuity between terminal 9 and 10 of key un-
lock warning switch connector, when the key is inserted
to the key cylinder or removed.
Replace key unlock warning switch.
2Check harness and connectors between ECU and key unlock warning switch, key un\
lock warn-
ing switch and body ground (See page IN±27).
Repair or replace harness or connector.
Proceed to next circuit inspection shown on ma-
trix chart (See page BE±371).
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BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±389
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NG
OK
1
2
Proceed to next circuit inspection shown on
matrix chart (See page BE±371)
Check luggage compartment door opener
main switch and opener switch.
Check harness and connectors between ECU
and main switch, opener switch and body
ground (See page IN±27). Repair or replace harness or
connector.
NG
OK Replace luggage compartment door
opener main switch and/or opener
switch.
WIRING DIAGRAM
Luggage Compartment Door Opener Main Switch and
Opener Switch Circuit
CIRCUIT DESCRIPTION
The luggage compartment door opener main switch is off when it
is pushed in, and the luggage compartment door opener switch is
on when it is pulled.
The ECU energizes the luggage compartment door opener motor
only when the main switch and opener switch are on together.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BE±390±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

OKNG
OKNG
INSPECTION PROCEDURE
1Check luggage compartment door opener main switch and opener switch.
C
OK
P
OK
C
Disconnect the luggage compartment door opener
main switch and opener switch connector.
Check luggage compartment door opener main switch.
Check continuity between terminals of main switch con-
nector.
Check luggage compartment door opener switch.
Check continuity between terminals of main switch and
opener switch connector.
Replace luggage compartment door opener main switch
and or opener switch.
2Check harness and connector between ECU and main switch, opener switch and bo\
dy ground
(See page IN±27).
Repair or replace harness or connector.
Proceed t next circuit inspection shown on matrix
chart (See page BE±371).
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BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±391
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1
2
NG
OK
Proceed to next circuit inspection shown on
matrix chart (See page BE±371)
Check door open detection switch.
Check harness and connectors between ECU and
door open detection switch, door open detection
switch and body ground (See page
IN±27).
Repair or replace harness or
connector.
NG
OK Replace door open detection
switch.
WIRING DIAGRAM
Door Open Detection Switch Circuit
CIRCUIT DESCRIPTION
The door open detection switch is built in the door lock assembly. It is on when the door is open and
off when the door is closed.
DIAGNOSTIC CHART
BE±392±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

OKNG
OKNG
INSPECTION PROCEDURE
1Check door open detection switch
C
OK
P1. Remove the door trim and service hole cover.
2. Disconnect door open detection switch connector.
Check continuity between terminals 3 and 6 of door
open detection switch connector, when the front door is
opened and closed.
Replace door open detection switch.
2Check harness and connectors between ECU and door open detection switch,\
door open
detection switch and body ground (See page IN±27).
Repair or replace harness or connector.
Proceed to next circuit inspection shown on
matric chart (See page BE±371).
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BODY ELECTRICAL SYSTEM Door Lock Control SystemBE±393
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HOW TO PROCEED WITH TROUBLESHOOTING
HINT: Troubleshooting of the wireless door lock control system is based on the \
premise that the door lock control
system is operating normally. Accordingly, before troubleshooting the wireless door lock control system, first
make certain that the door lock control system is operating normally.
Perform troubleshooting in accordance with the procedure on the followin\
g page.

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet of reference, ask the custome\
r in as much detail as pos-
sible about the problem.
\b PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem using
the ªProblem Simulation Methodº.
At this stage check whether the whole wireless door lock control system fa\
ils to operate, or whether only
some of the particular functions fail to operate.
 PRECHECK TYPE I,  PRECHECK TYPE II
Using the self diagnosis function of the wireless door lock ECU, perform Prec\
heck Type I to find out if the
system is normal (system non±operation due to external noise, etc.)\
or if the abnormality lies with the ve-
hicle. In Precheck Type II, locate if the cause of problem lies in the transmitter, the antenna or the vehicle.
Perform Precheck Type I when whole wireless door lock control system fails to operate only\
at a specific
locality.
Perform Precheck Type II when whole wireless door lock control system fails to operate no matter where
the locality is.
When only some functions of wireless door lock control system do not operate\
, proceed to [8] on the Matrix
Chart of Problem Symptoms.
 INSPECTION OF TRANSMITTER, [7] INSPECTION OF ANTENNA CIRCUIT
If it is found in Precheck Type II that the cause of the problem is in the transmitter or antenna, proc\
eed to
the appropriate pages and start troubleshooting.
 MATRIX CHART OF PROBLEM SYMPTOMS
Confirm the order of inspection for each applicable problem symptom on t\
he matrix chart.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection order confirmed in [8]. Judge
whether the cause of the problem is in the sensor, wire harness and connectors, or the ECU.
[10] REPAIR If the cause of the problem is found in [9]., perform repairs.
[11] CONFIRMATION TEST After completing repairs, confirm that the problem is eliminated and that all functions of the wireless door
lock control system are normal.
BE±442
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

PRECHECK TYPE I
In cases where the wireless door lock control system fails to operate only\
at a specific locality, perform this check
at that locality.
Open the driver's door
(Other doors remain closed).Using the door lock control switch, perform
ªlock, unlockº
*1 operation 10 times within 30
seconds.
How many times in 10 seconds is ªlock, un-
lockº
*1 operation performed automatically by
the ECU?
Noise is being produced at that locality.
*3
Vehicle is now receiving signals from a
transmitter of another vehicle (during
transmission from transmitter of another
vehicle).
Malfunction on vehicle side
(Proceed to Matrix Chart of Problem
Symptom on page
BE±454).
Does not
operate
2 times
3 times
Normal
*2
*1: Performing lock and unlock once counts as one time.
*2: If noise is not constantly produced at the locality being used and inspect\
ion is performed on an occasion when there is no noise, then it may happen that the system is judged normal.\
*3: If the conclusion is that noise is produced in the locality the vehicle is\
used, then transmitter use is limited in that locality. Limitations on usage are described below.
HINT:
Because the transmitter uses weak electromagnetic waves, it is easily affected by noise, so remote control with-
in the normal range becomes difficult.
To reduce the influence of noise, bring the transmitter as close as possib\
le to the back window glass (antenna
section), or touch (ground) the grooved key tip of the transmitter to\
the door key cylinder and then operate the
transmitter switch; this should make door lock remote control operation possible.
If door lock remote control operation is still not possible, insert the \
key in the door key cylinder and press the
transmitter switch.
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BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±445
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Open the driver's door
(Other doors remain closed).
Using the door lock control switch, perform
ªlock, unlockº
*1 operation 10 times with in
30 seconds.
Soon (less than 2 secs.) after performing
the above, continue to press the transmitter
switch for 10 seconds. How many times does ªlock, unlockº *1 op-
eration of all doors occur during the time the
transmitter is operated (approx. 10 secs.)? Malfunction on vehicle side
(Proceed to Matrix Chart of Problem
Symptom on page
BE±454).
Wrong transmitter parts (exclusive code
does not match).
[Replace transmitter and ROM in ECU.
(See page BE±449)]
Transmitter fault
(Inspect transmitter on page BE±447).
Close all doors.
Tune the FM radio to 94.9 MHz.
Inspect transmitter (See page BE±447).
Do all doors lock and unlock?
Is there noise on the radio while the trans-
mitter switch is being pushed? *2 Malfunction on antenna curcuit
(Inspect antenna circuit on page
BE±448).
Malfunction on vehicle side
(Proceed to Matrix Chart of Problem
Symptom on page BE±454).
3 times
2 timesDoes not
operate
YESYES
NO
NO Once

Disconnect the antenna cable from the ECU, directly insert
the transmitter (grooved section of key) and press the trans-
mitter switch. In this case do not let the transmitter come in
contact with the ECU case (because the transmitter will be
grounded).
PRECHECK TYPE II
Perform this check in cases where the wireless door lock control system fails t\
o operate anywhere.
*1: Performing lock and unlock once counts as one time.
*2: In some localities, inspection cannot be carried out because the local FM \
radio broadcast is also at 94.9 MHz. When this occurs, perform inspection using a portable radio in a place \
indoors free from the influence
of FM broadcasts.
BE±446
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BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

NGOK
INSPECTION OF TRANSMITTER
HINT: Perform this inspection only when transmitter is judged to be the fault\
y in precheck type II.
1Transmitter battery capacity check.
C
OK
P
HintThis inspection is not directly for the purpose of check-
ing the capacity of the transmitter battery, but is per-
formed when remote control operation becomes difficult
or impossible, in order to ascertain if this is caused by
low battery capacity.
1. Remove the transmitter screw.
2. /Remove the cover.
3. Remove the O±ring and battery.
1. Connect 2 new 1.5 V dry±cell batteries in series.Connect the battery
terminal to the battery re-
ceptacle side terminal and the battery  terminal to
the bottom terminal to provide 3 V to the transmitter.
2. In the condition (1), push the wireless door lock re- mote control switch on the side of the transmitter
body and operate the door lock by remote control.
Remove control operation possible.
Replace the battery for transmitter (See page BE±450).
Replace transmitter and ROM in ECU
(See page BE±450).
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BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±447
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WIRING DIAGRAM
Check defogger wire (See page BE±173).NG
OK Repair defogger wire.
Replace antenna pinjack cable and
capacitor.1
INSPECTION OF ANTENNA CIRCUIT
Antenna Circuit
CIRCUIT DESCRIPTION
The antenna receives the electromagnetic wave emitted by the transmitter and sends i\
t to the wireless
door lock ECU.
DIAGNOSTIC CHART
HINT: Perform this inspection only when vehicle antenna is judged to be fault\
y in initial check type II.
BE±448
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BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName