LEXUS SC400 1991 Service Repair Manual

±MEMO± BE±394
±
BODY ELECTRICAL SYSTEM Door Lock Control System
WhereEverybodyKnowsYourName

WIRELESS DOOR LOCK CONTROL
SYSTEM
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±439
WhereEverybodyKnowsYourName

DESCRIPTION
The wireless door lock control system is to lock and unlock all the doors a\
t a distance, transmitting a weak radio
wave from a transmitter contained in the master ignition key.
The weak radio wave (coded differently for each key) is sent to the receiver via the rear window defo\
gger wiring.
For the function of the component parts of this system, refer to the circui\
t description in circuit inspection.
PARTS LOCATION
BE±440±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

DESCRIPTION
The wireless door lock control system is to lock and unlock all the door\
s at a distance, transmitting a weak radio
wave from a transmitter contained in the master ignition key.
The weak radio wave (coded differently for each key) is sent to the receiver via the rear window defo\
gger wiring.
For the function of the component parts of this system, refer to the circui\
t description in circuit inspection.
PARTS LOCATION
BE±440±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName

±MEMO±
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±441
WhereEverybodyKnowsYourName

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

Vehicle Brought to WorkshopCustomer Problem Analysis P.BE±444
Problem Symptom Confirmation
Matrix Chart of Problem Symptoms P.BE±454 P.
IN±20
Circuit Inspection
P. BE±460 ~ BE±470
Identification of Problem
Repair
Confirmation Test END
Whole wireless door lock
Control system does not operate
Problem occurs
everywhereItems inside are titles of pages
in this manual, with the page number
indicated in the bottom portion.
See the indicated pages for detailed
explanations.
Symptom Simulation
Precheck Type I P. BE±445 Precheck Type II
P. BE±446
System is
Normal Inspection of
Transmitter
P. BE±449
Inspection of
Atenna Circuit P.BE±448
Transmitter Malfunction
Problem occurs
only at a
specific locality
Some functions of wireless door
lock control system do not operate
Malfunction on
vehicle side
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±443
WhereEverybodyKnowsYourName

CUSTOMER PROBLEM ANALYSIS CHECK SHEET
\
 
\

\
WIRELESS DOOR LOCK CONTROL System Check Sheet
Inspector 's
Name:
 


 


 

Registration No.
 


 Customer 's Name  Registration Year //
 


 


 

Frame No.
 


 


Date Vehicle
Brought In 

// 

Odometer Reading 


Km
Miles
 Date of Problem Occurrence\
 \
//
 

Frequency of Problem Occurrence
\
 
\

\

Constant  Sometimes ( times/per day, month)
 Once Only
 


Conditions at
 

Weather
\
 
\

\


Fine  Cloudy  Rainy  Snowy
 Various/Others
 


Conditions at
Time of Problem
Occurrence 

Outdoor Temperature
\
 
\

\


Hot  Warm  Cool
 Cold (Approx. 5F( 5C))
 


 

Place\
 
\

\

Everywhere  Specific Locality ( )
 

Date Transmitter Battery Last Replaced\
 
\

\
//
 \
 \

Whole wireless door lock control system does not operate
\

Whole wireless door lock control system does not operate.
 


\
 
\

\

Only door unlock operation is not possible.
 \
 \
Only door lock operation is not possible.
 


\
 
\

\

Only key confine prevention function is not possible.
 \
 \
 Wireless door lock function operates even when each door is opened.
 




\
 
\


\

\


Wireless door lock function incorrectly.
(Although one door is unlocked, when the transmitter
switch is pressed, all doors unlock.)
 





When RH door is unlocked.
 When LH door is unlocked.
 








\
 
\


\


\


\

\


Others
Problem Symptom
BE±444±
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.
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±445
WhereEverybodyKnowsYourName

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
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control System
WhereEverybodyKnowsYourName