Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Toyota Sienna 1998-2003 Approved FSM 05 eg cip0420
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DI-69
DIAGNOSTICS - ENGINE
DI4F5-02
DTC P0420 Catalyst System Efficiency Below Threshold
CIRCUIT DESCRIPTION
The ECM observes the waveform of the heated oxygen sensor located behind the catalyst to determine
whether the catalyst is performance has deteriorated.
If the catalyst is functioning normally, the waveform of the heated oxygen sensor located behind the catalyst
switches back and forth between rich and lean much more slowly.
When the waveform of the heated oxygen sensor located behind the catalyst alternates flatteringly between
rich and lean, it indicates that catalyst performance has deteriorated.
Waveform of
A/F Sensor Waveform of Heated Oxygen
Normal Catalyst Sensor Behind Catalyst
Abnormal Catalyst
A01674
DTC No. DTC Detecting Condition Trouble Area
S Three-way catalytic converter
After engine and catalyst are warmed up, and while vehicle is
S Open or short in heated oxygen sensor
driven within set vehicle and engine speed range, waveform of
(bank 1, sensor 2) circuit
P0420 heated oxygen sensor (bank 1, sensor 2) alternates flatteringly
S Heated oxygen sensor (bank 1, sensor 2)
between rich and lean
S Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
(2 trip detection logic)
S A/F sensors (bank 1, 2 sensor 1)
2001 SIENNA (RM787U)
Author : Date : 223
DI-70
DIAGNOSTICS - ENGINE
CONFIRMATION ENGINE RACING PATTERN
Engine Speed
(c) (d)
3,000 rpm
2,000 rpm
(b)
Idling
(a)
IG SW OFF Time
Warmed up 3 min. or so 2 sec. 2 sec.
Check
A00479
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Start engine and warm it up with all accessories switched OFF until water temp. is stable.
(c) Race the engine at 2,500 - 3,000 rpm for about 3 min.
(d) When racing the engine at 3,000 rpm for 2 sec. and 2,000 rpm for 2 sec. alternately, check the wave-
form of the heated oxygen sensor (bank 1 sensor 2).
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining
whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc.
at the time of the malfunction.
1 Are there any other codes (besides DTC P0420) being output?
YES Go to relevant DTC chart.
NO
2 Check gas leakage on exhaust system.
NG Repair or replace.
OK
2001 SIENNA (RM787U)
Author : Date : 224
DI-71
DIAGNOSTICS - ENGINE
3 Check A/F sensors (bank 1, 2 sensor 1) (See page SF-81 ).
NG Repair or replace.
OK
4 Check heated oxygen sensor (bank 1 sensor 2) (See page SF-82 ).
NG Repair or replace.
OK
Replace three-way catalytic converter.
2001 SIENNA (RM787U)
Author : Date : 225
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