1996 TOYOTA T100 check engine

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Waveform of Oxygen Sensor
before CatalystNormal CatalystWaveform of Oxygen Sensor
after Catalyst
P25762
Engine Speed
2500 − 3000 rpm
Idling
IG SW OFF
Warmed up3 minutesCheckTime (1)(3)
(4)
(2) DI−86
− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
DTC P0420 Catalyst System Efficiency Below Threshold
CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of
the oxygen sensor located after the catalyst to determine whether or not catalyst 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 oxygen sensor before the cata-
lyst.
But when both waveforms change at a similar rate, it indicates that catalyst performance has deteriorated.


DTC No.DTC Detecting ConditionTrouble Area
P0420
After engine and catalyst are warmed up, and while vehicle is
driven within set vehicle and engine speed range, waveforms
of heated oxygen sensors (bank 1 sensor 1, 2) have same
amplitude (2 trip detection logic)
TWC (Three−way catalytic converter)
Heated oxygen sensor (bank 1 sensor 1, 2)
CONFIRMATION ENGINE RACING PATTERN
DI0TW−02

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OX Signal Waveform (Oscilloscope)
1.0 V
0 V
200 msec. /Division
− DIAGNOSTICSENGINE (3RZ−FE)
DI−87
1996 TOYOTA T100 (RM449U)
(1) Connect the OBD ll scan tool or TOYOTA hand−held tester to the DLC3.
(2) Start engine and warm it up with all accessories switched OFF until the water temperature is stable.
(3) Race the engine at 2500 − 3000 rpm for about 3 min.
(4) After confirming that the waveform of the heated oxygen sensor, bank 1 sensor 1 (OX1), oscillate around
0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor bank 1 sensor 2 (OX2).
HINT:
If there is a malfunction in the system, the waveform of the
heated oxygen sensor bank 1 sensor 2 (OX2) is almost the
same as that of the heated oxygen sensor bank 1 sensor 1
(OX1) on the left.
There are some cases where, even though a malfunction
exists, the MIL may either light up or not light up.
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 DI−47).
NG Repair or replace.
OK
3 Check heated oxygen sensor (bank 1 sensor 2) (See page DI−53).
NG Repair or replace.
OK
Replace TWC (three−way catalytic convert-
er) (See page EM−104).

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FI7205 FI7206
A00071
VSV is ON VSV is OFFON
Air
E
FAir
EF
− DIAGNOSTICSENGINE (3RZ−FE)
DI−89
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
TOYOTA hand−held tester:
1 Connect TOYOTA hand−held tester and check operation of VSV for EVAP.
PREPARATION:
(a) Connect the TOYOTA hand−held tester to the DLC3.
(b) Turn the ignition switch ON and TOYOTA hand−held tes-
ter main switch ON.
(c) Select the ”ACTIVE TEST” mode on the TOYOTA hand−
held tester.
CHECK:
Check operation of VSV when it is operated by the TOYOTA
hand−held tester.
OK:
(1) VSV is ON:
Air flows from port E to port F.
(2) VSV is OFF:
Air does not flow from port E to port F.
OK Go to step 4.
NG
2 Check operation of VSV for EVAP (See page MF−44).
NG Replace VSV for EVAP.
OK
3 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and ECM (See page IN−26).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN−26).

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ON
For M/T
For A/TPRG (+)
PRG (+)
DI−90
− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
4 Check connection of vacuum hose (See Fig 1 in circuit description).
NG Repair or replace.
OK
Check and repair charcoal canister (See
page EC−5).
OBD II scan tool (excluding TOYOTA hand−held tester):
1 Check operation of VSV for EVAP (See page MF−43).
NG Replace VSV for EVAP.
OK
2 Check voltage between terminal PRG of ECM connector and body ground.
PREPARATION:
(a) Remove the right cowl side trim (See page MF−50).
(b) Turn the ignition switch ON.
CHECK:
Measuve voltage between terminal PRG of ECM connector and
body ground.
OK:
Voltage: 9 − 14 V
NG Check and repair harness or connector.
OK

Downloaded from www.Manualslib.com manuals search engine − DIAGNOSTICSENGINE (3RZ−FE)
DI−91
1996 TOYOTA T100 (RM449U)
3 Check connection of vacuum hose (See Fig 1 in circuit description).
NG Repair or replace.
OK
4 Check charcoal canister (See page EC−5).
NG Repair or replace.
OK
Check and replace ECM (See page IN−26).

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P24205 BE6653A00082
ON
For M/T
For A/TSP1 (+)
SP1 (+)
AT7809
4.5 − 5.5 V
0
Turn wheel
− DIAGNOSTICSENGINE (3RZ−FE)
DI−93
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
1 Check operation of speedometer.
CHECK:
Drive the vehicle and check if the operation of the speedometer in the combination meter is normal.
HINT:
The vehicle speed sensor is operating normally if the speedometer display is normal.
NG Check speedometer (See page BE−38).
OK
2 Check voltage between terminal SP1 of ECM connector and body ground.
PREPARATION:
(a) Remove the right cowl side trim (See page MF−50).
(b) Disconnect the cruise control ECU connector.
(c) Shift the shift lever to neutral.
(d) Jack up the rear wheels on one side.
(e) Turn the ignition switch ON.
CHECK:
Measure voltage between terminal SP1 of ECM connector and
body ground when the wheel is turned slowly.
OK:
Voltage is generated intermittently.
NG Check and repair harness and connector be-
tween combination meter and ECM.
OK
Check and replace ECM (See page IN−26).

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P24207
P24208
A00083
ON
For M/T
RSO (+) RSC (+)
For A/T
RSO (+) RSC (+)E7 Connector
E7 Connector
− DIAGNOSTICSENGINE (3RZ−FE)
DI−95
1996 TOYOTA T100 (RM449U)
INSPECTION PROCEDURE
1 Check air induction system (See page MF−1).
NG Repair or replace.
OK
2 Check voltage between terminals RSO and RSC of ECM connector and body
ground.
PREPARATION:
(a) Remove the right cowl side trim (See page MF−50).
(b) Disconnect the E7 connector of the ECM.
(c) Turn the ignition switch ON.
CHECK:
Measure voltage between terminals RSO and RSC of ECM
connector and body ground.
OK:
Voltage: 9 − 14 V
OK Go to step 4.
NG

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− DIAGNOSTICSENGINE (3RZ−FE)
1996 TOYOTA T100 (RM449U)
3 Check IAC valve (See page MF−31).
NG Replace IAC valve.
OK
Check for open and short in harness and con-
nector between R/B No.2 and IAC valve, IAC
valve and ECM (See page IN−26).
4 Check operation of IAC valve (See page MF−31).
NG Repair or replace IAC valve.
OK
Check and replace ECM (See page IN−26).