Page 478 of 1399
P22423
2
1 3
4
13
24
O
2
2
22 2
2
EB1
EA2
EFI
BR
R−Y
Y−RR
Y−R
1 7
R 3
5
1
E7
E5
E5
EFI Main
Relay
From BatteryEB
R/B No.2
14
32
BR−B
BR−B
BR−B WL
GR E6
E4E6
MRLY
B+
HT1
OX2
E1
HT2 E03
OX1
Heated Oxygen Sensor
(bank 1 sensor 1)
Heated Oxygen Sensor
(bank 1 sensor 2)
ECM
Y−R
Y−R
EC
32
14
E1E03
E1
7
−
DIAGNOSTICS ENGINE
DI−41
1996 LAND CRUISER (RM451U)
HINT:
After confirming DTC P0125 use the OBD II scan tool or TO YOTA hand held tester to confirm voltage output
of heated oxygen sensor (bank 1 sensor 1) from CURRENT DATA.
If voltage output of heated oxygen sensor (bank 1 sensor 1) is 0 V, heated oxygen sensor (bank 1 sensor
1) circuit may be open or short.
WIRING DIAGRAM
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Page 492 of 1399
P22424
Fusible Link
Battery
FL AM2
F7
EA2
6
11
3
1 IG Switch
W−RW
−R
B−R B−R
IH1
14B−R
B−R
B−R
B−R
B−R B−R 2
2
2
2
2
2 1
1
1
1
1
1 W−L
W−R
W−G Y
Y−R
Y−L
BR
BR E4
E4
E4
E4
E4 E4
E4
E4 11 12
25 2
1
15
13
26
EC
Injector #10
#20 #30
#40
#50
#60
E01
E02 ECM
No.1
No.2
No.3
No.4
No.5
No.6
FI6588 FI6538
A00064
10V/
Division
GND 10V/
Division
100 m sec./Division (Idling) GND(Magnification)
1 m sec./Division (Idling)
Injection duration
−
DIAGNOSTICS ENGINE
DI−55
1996 LAND CRUISER (RM451U)
WIRING DIAGRAM
Reference INSPECTION USING OSCILLOSCOPE
INJECTOR SIGNAL WAVEFORM
With the engine idling, measure between terminals #10 − #60 and E01 of ECM.
HINT:
The correct waveform is as shown.
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Page 506 of 1399

P22417
Exhaust
Gas
Intake Air
Chamber EGR
Valve
VSV
EGR
Vacuum
Modulator
ECM
Throttle
valve
P22426
BR
From Battery R/B No.2
R−Y
2
222
2
2
Y−R
EFI Main
Y−R
1
2
43
REA2
EZ1
EB12 7
VSV for EGR 21
YYL
−W
EZ14
EGR Gas T emp.
Sensor
21
G−Y
BR−BE7 E4
E4
E5 3
22
19
9
THG
E1
EGR
E2 5V
MRLY
ECM
R
EB
EFI
1
Relay
B+
E01
−
DIAGNOSTICS ENGINE
DI−69
1996 LAND CRUISER (RM451U)
DTC P0401 Exhaust Gas Recirculation Flow Insufficient
Detected
CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper \
quantity to suit the driving condi-
tions, into the intake air mixture to slow down combustion, reduce the combust\
ion temp. and reduce NOx
emissions. The amount of EGR is regulated by the EGR vacuum modulator ac\
cording to the engine load.
If even one of the following conditions is fulfilled, the VSV is
turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR valve, closing
the EGR valve and shutting off the exhaust gas (EGR cut− off).
Under the following conditions, EGR is cut to maintain driveabil-
ity.
Before the engine is warmed up.
During deceleration (throttle valve closed).
Light engine load (amount of intake air very small).
Engine racing.
DTC No.DTC Detecting ConditionTrouble Area
P0401
After the engine is warmed up and run at 80 km/h (50 mph)
for 3 to 5 minutes, the EGR gas temperature sensor value
does not exceed 38° C (100.4°F) above the ambient air tem-
perature. (2 trip detection logic) EGR valve stuck closed
Short in VSV circuit for EGR
Open in EGR gas temp. sensor circuit
EGR hose disconnected
ECM
WIRING DIAGRAM
DI5PK−02
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Page 527 of 1399
P22474
EBBR
22 22
1 3
4
2 2
2
R−Y R/B No.2
From BatteryR
Y−R
EA2
EB1
Y−RY −R
Y−R R
R−G
R−B
G−Y
Y−L
4
1
3 6
IAC Valve MRLY
E7
E4
E4
E4
E4 7 3
6
5
4
ISC1
ISC2
ISC3
ISC4 B+
E01
E01
E01
E01
EFI
2
5
EFI Main
Relay
7
1 ECM
A00202
ISC1
ISC2
ISC3
ISC4 A/C Switch OFF
→ ON
(IAC Valve Open)
20 V/Division
10 msec./Division
ISC1
ISC2
ISC3
ISC4 20 V/
Division
10 msec./Division
(IAC Valve Close)
A/C Switch ON →
OFF
FI6536
FI6537
DI−90
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
WIRING DIAGRAM
Reference: INSPECTION USING OSCILLOSCOPE
With the engine idling measure wavefoms between terminals
ISC1, ISC2, ISC3, ISC4 and E01 of ECM when A/C switch ON
or OFF.
HINT:
The correct waveforms are as shown.
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Page 529 of 1399
A00203
CloseOpen Battery
Battery
B1
S1
S2 B2S4
S3
B1
S1 S2 B2S4S3
P24670
P24671
DI−92
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
4 Check operation of the IAC valve .
PREPARATION:
Remove IAC valve (See page SF−51).
CHECK:
(a) Connect the positive (+) leak from the battery to terminals
5 (B1) and 2 (B2), and the negative ( −) lead to terminals
4 (S1), −1 (S2), −6 (S3), −3 (S4) in that order.
(b) Connect the positive (+) lead from the battery to terminals
5 (B1) and 2 (B2), and the negative ( −) lead to terminals
3 (S4), − 6 (S3), −1 (S2), − 4 (S1) in that order.
OK:
(1) The valve moves to close direction.
(2) The valve moves to open direction.
HINT:
The ACTIVE TEST mode of the T OYOTA hand−held tester can
be used to change the step of the IAC valve as desired.
NG Repair or replace IAC valve.
OK
Check and replace ECM (See page IN−28 ).
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P22475
BatteryFusible
Link
FL AM2
F7W−R
EA2
W−R
B−R B−R
EA2
B−R
B−W B−W
W−B
Distributor
Ignition
Coil 4
12
EA2
IH1
W−B
8 1
2
Noise
Filter 45
B 3
Igniter Tr2
2
1
IH2 IH2
B−G
B−G
B−Y B−YE4
E4 IGT
IGF Tr15V
ECM
1 3 11
6
IG Switch
1
EC
17 23
14 13
−
DIAGNOSTICS ENGINE
DI−97
1996 LAND CRUISER (RM451U)
DTC P1300 Igniter Circuit Malfunction
CIRCUIT DESCRIPTION
The ECM determines the ignition timing, turns on Tr1 at a predetermined angle ( °CA) before the desired
ignition timing and outputs and ignition signal (IGT) ”1” to the\
igniter.
Since the width of the IGT signal is constant, the dwell angle control circuit in \
the igniter determines the time
the control circuit starts primary current flow to the ignition coil based \
on the engine rpm and ignition timing
one revolution ago, that is, the time the Tr2 turns on.
When it reaches the ignition timing, the ECM turns Tr1 off and outputs the IGT signal ”O”.
This turns Tr2 off, interrupting the primary current flow and generating a high voltage i\
n the secondary coil
which causes the spark plug to spark. Also, by the counter electromotive forc\
e generated when the primary
current is interrupted, the igniter sends an ignition confirmation signal (IGF)\
to the ECM. The ECM stops fuel
injection as a fail safe function when the IGF signal is not input to the ECM.
DTC No.DTC Detecting ConditionTrouble Area
P1300No IGF signal to ECM for 6 consecutive IGT signals during
engine running Open or short in IGF or IGT circuit from igniter to ECM
Igniter
ECM
WIRING DIAGRAM
DI5PQ−02
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Page 540 of 1399
A15825
−
DIAGNOSTICS ENGINE
DI−103
1996 LAND CRUISER (RM451U)
DTC P1500 Starter Signal Circuit Malfunction
CIRCUIT DESCRIPTION
When the engine is cranked, the intake air flow is slow, so fuel vaporization is poor. A rich mixture is therefore
necessary in order to achieve good startability. While the engine is being cranked, the battery positive volt-
age is applied to terminal STA of the ECM. The starter signal is mainly used to increase the fuel inj\
ection
volume for the starting injection control and after −start injection control.
WIRING DIAGRAM
DI968−01
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Page 542 of 1399
P22477
BatteryFusible Link
E8
1 W
2 2
EFI
R/B No.2
R−YR−Y
EA2E7ECM
BATT
2
FL MAIN
2
−
DIAGNOSTICS ENGINE
DI−105
1996 LAND CRUISER (RM451U)
DTC P1600 ECM BATT Malfunction
CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for
use by the DTC memory and air −fuel ratio adaptive control value memory, etc.
DTC No.DTC Detecting ConditionTrouble Area
P1600Open in back up power source circuitOpen in back up power source circuit
ECM
HINT:
If DTC P1600 appear, the ECM does not store another DTC.
WIRING DIAGRAM
DI5PT−02
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