ECU LEXUS SC400 1991 Service Repair Manual

PARTS REPLACEMENT
WIRELESS DOOR LOCK ECU REMOVAL
AND INSTALLATION
1. REMOVE WIRELESS DOOR LOCK ECU(a) Remove the rear seat.
(b) Remove the RH quarter trim panel.
(c) Disconnect the connectors.
(d) Remove the ECU.
2. INSTALL WIRELESS DOOR LOCK ECU For installation, follow the removal procedure in reverse.
WIRELESS DOOR LOCK ECU AND
TRANSMITTER REPLACEMENT
Disassembly and assembly of the wireless door lock ECU
and transmitter includes details of spare parts and replace-
ment procedure for defective parts found through trouble-
shooting.
Each part is a precision electronic component so handle with
care.
Destroy old ROM and transmitter to prevent reuse.
1. SPARE PARTS AND REPLACEMENT PROCEDURE FOR MALFUNCTIONING PARTS
(For malfunctioning transmitter)
(a) Prepare the new transmitter (with ROM).
(b) Remove the ECU from the vehicle.
(c) Remove the ROM from the ECU.
(d) Install the new ROM into the ECU.
(e) Install the ECU into the vehicle.
(f) Check that door lock remote control operation works.
(g) Cut the new key to the shape of the replaced key.
(For non±functioning battery)
(a) Prepare new battery (with O±ring).
(b) Remove battery and O±ring from transmitter.
(c) Install new battery and O±ring into transmitter.
±
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(For malfunctioning ECU)
(a) Prepare the new ECU (without ROM).
(b) Remove the ECU from the vehicle.
(c) Remove the ROM from the ECU.
(d) Install the ROM into the new ECU.
(e) Install the new ECU into the vehicle.
2. REMOVAL OF ROM FROM ECU (a) Remove the cover from the hole for ROM insertion.
(b) Using long nosed pliers, grasp the center of the print
board (ROM) and remove it.
NOTICE:
w When replacing the ROM, always disconnect the
ECU connector first.
w When removing the ROM, always grasp the board
and do not touch the IC parts or print wiring on the
board.
(c) Insert the new print board (ROM) along the rails on both sides and push it in with your finger until the terminal on
the end is completely inserted.
(d) Install the cover to the hole for ROM insertion.
3. REPLACEMENT OF BATTERY FOR TRANSMITTER (a) Remove the screw from the transmitter.
(b) Remove the cover.
BE±450
±
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Terminals of ECU
WIRING DIAGRAM
No.SymbolTerminal NameNo.SymbolTerminal Name
W8±1+BPower SourceW8±6KSWKey Unlock Warning Switch
W8±2LSWD1Door Unlock Detection Switch LHW8±7EGround
W8±3LSWPDoor Unlock Detection Switch RHW8±8
W8±4UL1Door Key Lock and Unlock SwitchW8±9LSWD2Door Lock Motor LH
W8±5L1Door Key Lock and Unlock SwitchW8±10DSWDDoor Open Detection Switch
BE±452±
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STANDARD VALUE OF ECU TERMINAL
 

Terminals
 

Symbols
 

Wiring
color 

Condition
 

Standard
Value
 

W8±1
eW8±7
 

+B1
eE
 

R±L
eW±B
 

Wireless door lock main switch ON 

10 ~ 14 V 


W8±1eW8±7 


+B1eE 


R±LeW±B 

Wireless door lock main switch OFF
 

Below 1 V
 W8±2
eBody LSWD1 eBody L±W eBody Door lock knob of driver's door LOCK 8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of driver's door UNLOCK Below 1 V
 W8±3 eBody LSWP eBody P±B eBody Door lock knob of assistant's door LOCK 8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of assistant's door UNLOCK Below 1 V
 


W8 4
eBody
 


UL1
eBody
 


GW
eBody
 


Turn ignition switch ON,
Key operate switch Left and Right UNLOCK 


Below 1 V 


W8±4
eBody
Ground 


UL1
eBody
Ground 


G±W
eBody
Ground 


Turn ignition switch ON
Key operate switch Left or Right UNLOCK 


Below 1 V
    Except above mention 8 ~ 10 V
 

W8±5
eBody
 

L1
eBody
 

G±Y
eBody
 

Turn ignition switch, ON
Key operate switch Right LOCK 

Below 1 V
 


y
Ground 


y
Ground 


y
Ground 

Turn ignition switch ON,
Except above mention 

8 ~ 10 V
 W8±6
eBody KSW eBody Ye Body Ignition key insert key cylinder Below 1 V 

y
Ground 

y
Ground 

y
Ground 
Ignition key pull out key cylinder 
10 ~ 14 V 

W8±7
eBody
Ground
 

E
e Body
Ground
 

W±B
eBody
Ground
 

Always
 

Below 1 V
 

W8±9
eBody
 

LSWD2
eBody
 

W±L
eBody
 

Door lock knob of driver's door LOCK
 

8 ~ 10 V
 
y
Ground 
y
Ground 
y
Ground Door lock knob of driver's door UNLOCK Below 1 V
    Door open detection switch Left and Right ON 
 W8±10
eBody DSWD eBody G±L eBody Door open detection switch Left or Right ON Below 1 V
 
y
Ground 
y
Ground 
y
Ground Door open detection switch Left or Right OFF 
    Door open detection switch Left and Right OFF 10 ~ 14 V
±
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MATRIX CHART OF PROBLEM SYMPTOMS
Perform troubleshooting of the circuits for the applicable problem symptom in t\
he order given in the chart below.
Proceed to the page located for each circuit.
HINT:
w Troubleshooting of the wireless door lock control system is based on the premise that the d\
oor 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.
w If the instruction ºProceed to next circuit inspection shown on matrix \
chartº is given in the flow chart for each
circuit, proceed to the circuit with the next highest number in the table to con\
tinue the check.
w If the trouble still reappears even though there are no abnormalities in a\
ny of the other circuits, then check
and replace the Wireless Door Lock ECU as the last step.
See page
BE±460BE±462BE±464BE±466BE±468BE±470IN±32
SymptomSuspect
Area
ECU Power Source CircuitDoor Unlock Detection Switch CircuitDoor Key Lock and Unlock Swtich Circuit
(Unlock Side)Door Key Lock and Unlock Swtich Circuit
(Lock Side)Key Unlock Warning Switch CircuitDoor Open Detection Swtich CircuitWireless Door Lock ECU
All functions of wireless door lock control system do not
operate.134526
Only door unlock operation is not possible
(Lock operation is possible).213
Only door lock operation is not possible
(Unlock operation is possible).12
Only transmitter misoperation prevention function is not
possible12
Wireless door lock function operates even when each door is
opened.12
Wireless door lock functions incorrectly.
(Although one door is unlocked, when the transmitter switch
is pressed, all doors unlock.)
12
BE±454±
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WIRING DIAGRAM
Check DOME fuse.NG
OK Check for short in all the harness
and components connected to
DOME fuse.
(See attached wiring diagram)
Check voltage between terminals +B and
E of wireless door lock ECU connector.
Check for open in harness and connector
between terminal E of ECU and body
ground (See page IN±27).
Check and repair harness and connector
between ECU and main switch, main
switch and battery. Check wireless door lock main switch. Proceed to next circuit inspec-
tion shown on matrix chart
(See page
BE±454).
Repair or replace harness or
connector.
Replace wireless door lock main
switch.
NG
NG
NG
OK
OK OK1
2
3
4
CIRCUIT INSPECTION
ECU Power Source Circuit
CIRCUIT DESCRIPTION
When the wireless door lock main switch is ON, battery voltage is applied to\
terminal +B of the
wireless door lock ECU, causing the ECU to operate.
When the wireless door lock main switch is OFF, battery voltage is not applied to terminal +B and the
ECU does not operate.
DIAGNOSTIC CHART
BE±460±
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OKNG
NGOK
OKNG
OKNG
INSPECTION PROCEDURE
1Check DOME fuse.
Check for short in all the harness and components con-
nected to DOME fuse (See attached wiring diagram).
2Check voltage between terminals +B and E of ECU connector.
C
OK
P1. Remove the rear seat and RH quarter trim panel.
2. Remove the ECU.
Measure voltage between terminals +B and E of ECU
connector, when wireless door lock main switch is on
and off.
Wireless door lock main switchON
OFF Voltage
10 ± 14 V
Below 1 V
Proceed to
next circuit inspection shown on matrix chart
(See page BE±454).
3Check for open in harness and connector between terminal E of ECU and bo\
dy ground
(See page IN±27).
Repair or replace harness or connector.
4Check wireless door lock main switch.
C
OK
P1. Remove the instrument lower finish panel.
2. Remove wireless door lock main switch.
3. Disconnect the connector.
Measure resistance between terminals of wireless door
lock main switch connector, when main switch is on and
off.
Wireless door lock main switch
ON
OFF Resistance
Continuity
1M or higher
Replace wireless door lock main switch.
Check and repair harness and connector between
ECU and main switch, main switch and battery.
±
BODY ELECTRICAL SYSTEM Wireless Door Lock Control SystemBE±461
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WIRING DIAGRAM
Door Unlock Detection Switch Circuit
CIRCUIT DESCRIPTION
The door unlock detection switch is built into the door lock motor assembly\
. The switch is OFF when the door
lock knob is in Lock position, and is ON when the knob is in Unlock posi\
tion.
Furthermore, the door unlock detection switch circuit has terminal + B connected ins\
ide the theft deterrent ECU,
when the door unlock detection switch is OFF, battery positive voltage is applied to the terminal of the door un-
lock detection switch circuit of the wireless door lock ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
NGOK
Proceed to next circuit inspec-
tion shown on matrix chart (See
page
BE±454 ).
Check voltage between terminals LSWD1
LSWP and LSWD2 of ECU connector and
body ground.
Check and repair harness and connector
between ECU and door unlock detection
switch.
1
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NGOK
INSPECTION PROCEDURE
1Check voltage between terminals LSWD1, LSWP and LSWD2 of ECU connector a\
nd body
ground.
C
OK
P1. Remove the rear seat and RH quarter trim panel.
2. Remove the ECU.
3. Turn ignition switch on.
Measure voltage between terminals LSWD1, LSWP
and LSWD2 of ECU connector and body ground, when
the respective door lock knob involved is pushed to the
lock side.
Voltage: 8 ± 10 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±454).
Check and repair harness and connector between ECU and door unlock detec\
tion switch.
±
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WIRING DIAGRAM
Door Key Lock and Unlock Switch Circuit (Unlock Side)
CIRCUIT DESCRIPTION
The door key lock and unlock switch is built into the door key cylinder. When the key is turned to the lock side,
the lock terminal of the switch is grounded, and when the key is turned to the unlock side the unlock terminal
is grounded.
Furthermore, the door key lock and unlock switch circuit has terminal +B\
connected inside the theft deterrent
and door lock ECU, when neither the lock or unlock terminal of the door key\
lock and unlock switch are grounded,
battery positive voltage is applied to the door key lock and unlock switch circuit of the wireless d\
oor lock ECU.
(Tr inside the ECU coming ON causes the wireless door lock ECU to output a \
signal to unlock all the doors.)
DIAGNOSTIC CHARTDIAGNOSTIC CHART
NGOK
Proceed to next circuit inspec-
tion shown on matrix chart (See
page
BE±454 ).
Check voltage between terminal UL1 of
ECU connector and ground.
Check and repair harness and connector
between ECU and key door key lock and
unlock switch.
1
BE±464±
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