TOYOTA LAND CRUISER 1996 J80 Workshop Manual

P23431
Waveform of Oxygen Sensor
Before CatalystNormal
CatalystWaveform of Oxygen Sensor
After Catalyst
DI−84
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
DTC P0420 Catalyst System Efficiency Below Threshold
CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catal\
yst with the waveform of
the oxygen sensor located after the catalyst to determine whether or not ca\
talyst performance has deterio-
rated.
Air−fuel ratio feedback compensation keeps the waveform of the oxygen sensor\
before the catalyst repeat-
edly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back
and forth between rich and lean much more slowly than the waveform of the o\
xygen sensor before the cata-
lyst.
But when both waveforms change at a similar rate, it indicates that catalyst perf\
ormance has deteriorated.


DTC No.DTC Detecting ConditionTrouble Area
P0420
After the engine is warmed up and the vehicle driven for 6
mins. at 30 − 83 km/h (19 − 52 mph), the waveforms of the
heated oxygen sensors, bank 1 sensor 1 and bank1 sensor 2,
have the same amplitude Front exhaust pipe (front catalyst) and rear TWC (rear cata-
lyst)
 Heated oxygen sensor
DI5PM−02
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A00560
Vehicle Speed50 − 65 km/h
Idling
IG SW OFF (1)(2) (3)
Warmed up 5 − 10 mins.
Time
(31 −
40mph)
−
DIAGNOSTICS ENGINE
DI−85
1996 LAND CRUISER (RM451U)
CONFIRMATION ENGINE RACING PATTERN
(1) Connect the OBDII scan tool or TOYOTA hand−held tester to the DLC 3.
(2) Start and warm up the engine with all accessories switched OFF.
(3) Run the vehicle at 50 − 65 km/h (31 − 40 mph) for 5 − 10 mins.
HINT:
If a malfunction exists, the MIL will light up during step (3).
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DI−86
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
INSPECTION PROCEDURE
1 Are there any other codes (besides DTC P0420) being output?
YES Go to relevant DTC chart.
NO
2 Check heated oxygen sensor (bank 1 sensor 1) (See page SF−64 ).
NG Repair or replace.
OK
3 Check heated oxygen sensor (bank 1 sensor 2) (See page SF−64 ).
NG Repair or replace.
OK
Replace front exhaust pipe (front catalyst)
and rear TWC (rear catalyst) (See page
EM−11 0 ).
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P22487
No.1 Vehicle
Speed SensorCombination
Meter ECM
4−pulse
4−pulse
P22473
Combination Meter
3
C13 L−WL
−W8
E7 SPD ECM
5V
E1
From Cruise Control ECU
−
DIAGNOSTICS ENGINE
DI−87
1996 LAND CRUISER (RM451U)
DTC P0500 Vehicle Speed Sensor Malfunction
CIRCUIT DESCRIPTION
The vehicle speed sensor outputs a 4 − pulse signal for every revolution of the rotor shaft, which is rotated
by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectan-
gular wavefrom by the waveform shaping circuit inside the combination meter, it is then transmitted to the
ECM. The ECM determines the vehicle speed based on the frequency of thes\
e pulse signals.
DTC No.DTC Detecting ConditionTrouble Area
P0500
No vehicle speed sensor signal to ECM under conditions (a)
and (b):
(2 trip detection logic)
(a) Park/neutral position switch is OFF.
(b) Vehicle is being driven. Open or short in No.1 vehicle speed sensor circuit
 No.1 vehicle speed sensor
 Combination meter
 ECM
WIRING DIAGRAM
DI5PN−02
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A00176
ONSPD
(+)
(−)
BE6653
P24668
AT7809
9 − 14 V
0
Turn the wheel
DI−88
−
DIAGNOSTICS ENGINE
1996 LAND CRUISER (RM451U)
INSPECTION PROCEDURE
1 Check operation of speedometer.
CHECK:
Drive the vehicle and check if the operation of the speedmeter in the co\
mbination meter is normal.
HINT:
The vehicle speed sensor is operating normally if the speedometer displa\
y is normal.
NG Check speedometer circuit (See page BE−2 ).
OK
2 Check voltage between terminal SPD of ECM connector and body ground.
PREPARATION:
(a) Remove instrument panel speaker No.1 panel (See page SF−65 ).
(b) Disconnect cruise control ECU connector.
(c) Shift the shift lever to neutral.
(d) Jack up a rear wheels on one side.
(e) Turn ignition switch ON.
CHECK:
Measure voltage between terminal SPD of ECM connector and
body ground when the wheel is turned slowly.
OK:
Voltage is generated intermittently.
NG Check and repair harness and connector between combination meter and ECM.
OK
Check and replace ECM (See page IN−28 ).
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P22234
From
Air
CleanerSignals ECM IAC ValveValve ShaftRotor
To Cylinders
Throttle Valve
Intake Air
Chamber
Coils
Valve
−
DIAGNOSTICS ENGINE
DI−89
1996 LAND CRUISER (RM451U)
DTC P0505 Idle Control System Malfunction
CIRCUIT DESCRIPTION
The step motor type IAC valve is located in front of the intake
air chamber. Intake air bypassing the throttle valve is directed
to the IAC valve through a passage. A step motor is built into
the IAC valve. It consists of four coils, a magnetic rotor, valve
shaft and valve. When current flows to the coils due to signals
from the ECM, the rotor turns and moves the valve shaft forward
or backward, changing the clearance between the valve and
the valve seat. In this way the intake air volume bypassing the
throttle valve is regulated, controlling the engine speed. There
are 125 possible positions to which the valve can be opened.
DTC No.DTC Detecting ConditionTrouble Area
P0505Idle speed continues to vary greatly from the target speed
(2 trip detection logic)
 IAC valve is stuck or closed
 Open or short in IAC valve circuit
 Open or short in A /C signal circuit
 Air intake (hose loose)
DI5PO−02
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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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A00178
ONISC1 ISC3ISC2 ISC4
E4 connector
(−) (+)
BE6653
P24669
−
DIAGNOSTICS ENGINE
DI−91
1996 LAND CRUISER (RM451U)
INSPECTION PROCEDURE
1 Check air induction system (See page SF−1 ).
NG Repair or replace.
OK
2 Check voltage terminals ISC1, ISC2, ISC3, ISC4, of ECM connector and bod\
y ground.
PREPARATION:
(a) Remove instrument panel speaker No.1 panel (See page
SF−65 ).
(b) Disconnect the E4 connector of ECM.
(c) Turn ignition switch ON.
CHECK:
Measure voltage between terminals ISC1, ISC2, ISC3, ISC4 of
ECM connector and body ground.
OK:
Voltage: 9 − 14 V
OK Go to step 4.
NG
3 Check IAC valve (See page SF−49 ).
NG Replace IAC valve.
OK
Check for open and short in harness and co −nnector between EFI main relay (Marking:EFI) and
IAC valve and ECM (See page IN−28).
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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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−
DIAGNOSTICS ENGINE
DI−93
1996 LAND CRUISER (RM451U)
DTC P0510 Closed Throttle Position Switch Malfunction
CIRCUIT DESCRIPTION
Refer to DTC P0120 (Throttle/Pedal Position Sensor/Switch ”A” Circuit \
Malfunction) on page DI−35.
DTC No.DTC Detecting ConditionTrouble Area
P0510
The closed throttle position switch does not turn ON or OFF
even once when the vehicle is driven
(2 trip detection logic)Open or short in closed throttle position switch circuit
 Closed throttle position switch
 ECM
HINT:
After confirming DTC P0510 use the TOYOTA hand−held tester to confirm the closed throttle position switch
signal from ”CURRENT DATA”.
Throttle ValveClosed Throttle Position Switch SignalMalfunction
Fully closedOFFOpen circuit
Fully openONShort circuit
WIRING DIAGRAM
Refer to DTC P0120 (Throttle/Pedal Position Sensor/Switch ”A” Circuit Malfunction) on page DI−35 for WIR-
ING DIAGRAM.
INSPECTION PROCEDURE
HINT:
If DTCs P0110 (Intake Air Temp. Circuit Malfunction), P0115 (Engine Coolant Temp. Circuit Malfunction),
P0120 (Throttle/Pedal Position Sensor/Switch ”A” Circuit Malfunction)\
are output simultaneously, E2 (Sen-
sor Ground) may be open.
TOYOTA hand −held tester
1 Connect the TOYOTA hand −held tester and read CTP switch signal.
PREPARATION:
(a) Remove the fuse cover on the instrument panel.
(b) Connect OBD II scan tool or TOYOTA hand−held tester to the DLC3.
(c) Turn ignition switch ON and OBD II scan tool or TOYOTA hand−held tester main switch ON.
CHECK:
Read CTP switch signal on TOYOTA hand −held tester.
RESULT:
Throttle ValveClosed Throttle Position Switch SignalMalfunction
Fully closedOFFOpen circuit: Go to step 2
Fully openONShort circuit: Go to step 4
DI5PP−02
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