2000 TOYOTA CAMRY O2 sensor

± DIAGNOSTICSENGINE (5S±FE)
DI±113
348 Author: Date:
DTC P0402 Exhaust Gas Recirculation Flow Excessive
Detected
CIRCUIT DESCRIPTION
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on page DI±105.
DTC No.DTC Detecting ConditionTrouble Area
P0402
After engine is warmed up, conditions (a) and (b) continue:
(a) Intake manifold absolute pressure is larger than value cal-
culated by ECM while EGR system is ON
(b) Misfiring is detected during idling
(2 trip detection logic)
EGR valve stuck open

Vacuum or EGR hose is connected to wrong post

Manifold absolute pressure sensor

ECM
WIRING DIAGRAM
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on DI±105.
SYSTEM CHECK DRIVING PATTEM
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on DI±105.
INSPECTION PROCEDURE
HINT:

If DTC P0105 (Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction), P0106 (Manifold
Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem) and P0402 (Exhaust
Gas Recirculation Flow Excessive Detected) are output simultaneously, perform troubleshooting of
DTC P0105 first.

If DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) and P0402 (Exhaust Gas Recir-
culation Flow Excessive Detected) are output simultaneously, perform troubleshooting of DTC P0402
first.

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 Check connection of vacuum hose and EGR hose (See page EC±12).
NG Repair or replace.
OK
DI016±04

± DIAGNOSTICSENGINE (5S±FE)
DI±115
350 Author: Date:
6 Check EGR vacuum modulator (See page EC±12).
NG Repair or replace.
OK
7 Check manifold absolute pressure sensor (See page SF±53).
NG Repair or replace.
OK
Check and replace ECM (See page IN±31).

FI7081
Waveform of Heated Oxygen
Sensor before CatalystNormal CatalystWaveform of Heated Oxygen
Sensor behind Catalyst DI±116
± DIAGNOSTICSENGINE (5S±FE)
351 Author: Date:
DTC P0420 Catalyst System Efficiency Below Threshold
(Except California Spec.)
CIRCUIT DESCRIPTION
The ECM compares the waveform of the heated oxygen sensor located before the catalyst with the wave-
form of the heated oxygen sensor located behind the catalyst to determine whether or not catalyst perfor-
mance has deteriorated.
Air±fuel ratio feedback compensation keeps the waveform of the heated oxygen sensor before the catalyst
repeatedly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the heated oxygen sensor behind the catalyst switches
back and forth between rich and lean much more slowly than the waveform of the heated oxygen sensor
before the catalyst.
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)
Three±way catalytic converter

Open or short in heated oxygen sensor circuit

Heated oxygen sensor
DI1JX±03

FI7132
Engine Speed
2,500 ~ 3,000 rpm
Idling
IG SW OFF
Warmed up3 min. or soCheck
Time (a)(c)
(d)
(b)
FI6514
OX Signal Waveform (Oscilloscope)
1.0 V
0 V
200 msec. /Division
± DIAGNOSTICSENGINE (5S±FE)
DI±117
352 Author: Date:
CONFIRMATION ENGINE RACING PATTERN
(a) Connect the TOYOTA hand±held tester to the DLC3, or connect the probe of the oscilloscope between
terminals OX1, OX2 and E1 of the ECM connector.
(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) After confirming that the waveforms 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.

DI±118
± DIAGNOSTICSENGINE (5S±FE)
353 Author: Date:
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
3 Check heated oxygen sensor (bank 1 sensor 1) (See page DI±66).
NG Repair or replace.
OK
4 Check heated oxygen sensor (bank 1 sensor 2) (See page DI±77).
NG Repair or replace.
OK
Replace three±way catalytic converter.

A00357
Waveform of
A/F SensorNormal CatalystWaveform of Heated Oxygen
Sensor behind Catalyst
Abnormal Catalyst
± DIAGNOSTICSENGINE (5S±FE)
DI±119
354 Author: Date:
DTC P0420 Catalyst System Efficiency Below Threshold
(Only for California Spec.)
CIRCUIT DESCRIPTION
The ECM observes the waveform of the heated oxygen sensor located behind the catalyst to determine
whether the catalyst 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 flutteringly between
rich and lean, 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, waveform of
heated oxygen sensor (bank 1 sensor 2) alternates flutteringly
between rich and lean
(2 trip detection logic)
Three±way catalytic converter

Open or short in heated oxygen sensor (bank 1 sensor 2)
circuit

Heated oxygen sensor (bank 1 sensor 2)

Open or short in A/F sensor circuit

A/F sensor
DI1JY±03

A00479
Engine Speed
3,000 rpm
Idling
IG SW OFF
Warmed up
3 min. or so
CheckTime (a)(c) (d)
(b) 2,000 rpm
2 sec. 2 sec.
DI±120
± DIAGNOSTICSENGINE (5S±FE)
355 Author: Date:
CONFIRMATION ENGINE RACING PATTERN
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Start the 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

± DIAGNOSTICSENGINE (5S±FE)
DI±121
356 Author: Date:
3 Check A/F sensor (See page DI±66).
NG Repair or replace.
OK
4 Check heated oxygen sensor (bank 1 sensor 2) (See page DI±77).
NG Repair or replace.
OK
Replace three±way catalytic converter.