Page 2529 of 4770
± DIAGNOSTICSENGINE (5S±FE)
DI±109
344 Author: Date:
4 Check EGR system (See page EC±12).
NG Repair or replace.
OK
5 Check EGR vacuum modulator (See page EC±12).
NG Repair or replace.
OK
6 Check EGR valve (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).
Page 2530 of 4770
A03017
A03418
ON
E9 Connector
EGR
OFF
Air
FilterON
Air
Air
E
G E
VSV is ON
VSV is OFF Air
G w/o Immobiliser
w/ Immobiliser
OFF
ON EGR
E8 Connector
DI±110
± DIAGNOSTICSENGINE (5S±FE)
345 Author: Date:
OBD II scan tool (excluding TOYOTA hand±held tester):
1 Check connection of vacuum hose and EGR hose (See page EC±12).
NG Repair or replace.
OK
2 Check VSV for EGR.
PREPARATION:
(a) Remove the glove compartment (See page SF±64).
(b) Disconnect the E9 connector (w/o immobilizer) or E8 con-
nector (w/ immobilizer) the ECM.
(c) Turn the ignition switch ON.
CHECK:
Check VSV function
(1) Connect between terminal EGR of the ECM con-
nector and body ground (ON).
(2) Disconnect between terminal EGR of the ECM con-
nector and body ground (ON).
OK:
(1) VSV is ON:
Air from port E is flowing out through the air filter.
(2) VSV is OFF:
Air from port E is flowing out port G.
OK Go to step 4.
NG
Page 2531 of 4770
± DIAGNOSTICSENGINE (5S±FE)
DI±111
346 Author: Date:
3 Check operation of VSV for EGR (See page SF±43).
NG Replace VSV for EGR.
OK
Check for open and short in harness and con-
nector between engine room J/B No.2 and
ECM (See page IN±31).
4 Check EGR system (See page EC±12).
NG Repair or replace.
OK
5 Check EGR vacuum modulator (See page EC±12).
NG Repair or replace.
OK
6 Check EGR valve (See page EC±12).
NG Repair or replace.
OK
Page 2532 of 4770
DI±112
± DIAGNOSTICSENGINE (5S±FE)
347 Author: Date:
7 Check manifold absolute pressure sensor (See page SF±53).
NG Repair and replace.
OK
Check and replace ECM (See page IN±31).
Page 2533 of 4770

± 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
Page 2534 of 4770
DI±114
± DIAGNOSTICSENGINE (5S±FE)
349 Author: Date:
2 Check EGR valve (See page EC±12).
NG Repair or replace.
OK
3 Check VSV for EGR*.
*: If you have TOYOTA hand±held tester, see page DI±105, step 2.
If you have no TOYOTA hand±held tester, see page DI±105, step 2.
OK Go to step 4.
NG
4 Check operation of VSV for EGR (See page SF±43).
NG Replace VSV for EGR.
OK
Check for open and short in harness and con-
nector between engine room J/B No.2 and
ECM (See page IN±31).
5 Check EGR system (See page EC±12.)
NG Repair or replace.
OK
Page 2535 of 4770
± 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).
Page 2536 of 4770

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