Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Toyota 4Runner 1996-2003 Approved SIL techinfo.toyota.com ileaf 02toyrm 02toypdf 02rmsour 2002 024runne di eg5vzfe cip0420o
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DI-70
DIAGNOSTICS - ENGINE (5VZ-FE)
DI5C9-06
DTC P0420 Catalyst System Efficiency Below Threshold
(Bank 1)
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 flatter-
ingly between rich and lean, it indicates that catalyst performance has deteriorated.
Waveform of
A/F Sensor Normal Catalyst Waveform of Heated Oxygen
Sensor Behind Catalyst
Abnormal Catalyst
A07722
DTC No. DTC Detecting Condition Trouble Area
After engine and catalyst are warmed up, and while vehicle is S Gas leakage on exhaust system
driven within set vehicle and engine speed range, waveform of S A/F sensor (bank 1 sensor 1)
P0420
heated oxygen sensor (bank 1 sensor 2) alternates flatteringly S Heated oxygen sensor (bank 1 sensor 2)
between rich and lean (2 trip detection logic) S Three-way catalytic converter
2002 4RUNNER (RM887U)
Author : Date : 246
DI-71
DIAGNOSTICS - ENGINE (5VZ-FE)
CONFIRMATION ENGINE RACING PATTERN
Engine Speed
(3) (4)
3,000 rpm
2,000 rpm
(2)
Idling
(1)
IG SW OFF Time
Warmed up 3 min. or so 2 sec. 2 sec.
Check
A00479
(1) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(2) Start the engine and warm it up with all the accessories switched OFF until the water temperature
is stable.
(3) Race the engine at 2,500 - 3,000 rpm for about 3 min.
(4) When racing the engine at 3,000 rpm for 2 sec. and 2,000 rpm for 2 sec. alternately, check the
waveform 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 was warmed up or not, the air-fuel ratio was 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
2002 4RUNNER (RM887U)
Author : Date : 247
DI-72
DIAGNOSTICS - ENGINE (5VZ-FE)
3 Check A/F sensor (bank 1 sensor 1) (See page SF-51 ).
NG Repair or replace.
OK
4 Check heated oxygen sensor (bank 1 sensor 2) (See page SF-52 ).
NG Repair or replace.
OK
Replace three-way catalytic converter.
2002 4RUNNER (RM887U)
Author : Date : 248
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