TOYOTA CAMRY 1999 Service Repair Manual

P23871
EGR Gas Temp. Sensor
Connector
± DIAGNOSTICSENGINE (1MZ±FE)
DI±299
534 Author: Date:
OBDII scan tool (excluding TOYOTA hand±held tester)
1 Check resistance of EGR gas temp. sensor.
PREPARATION:
Disconnect the EGR gas temp. sensor connector.
CHECK:
Measure resistance between terminals of the EGR gas temp.
sensor connector.
OK:
Resistance: 2.5 kW ~ 600 kW
(Not immediately after driving)
HINT:
If there is open circuit, ohmmeter indicates 720 kW or more.
If there is short circuit, ohmmeter indicates 200 W or less.
NG Replace EGR gas temp. sensor.
OK
2 Check for open and short in harness and connector between EGR gas temp.
sensor and ECM (See page IN±31).
NG Repair or replace harness or connector.
OK
3 Check connection and blockage of vacuum hose (See page EC±2).
NG Repair or replace vacuum hose.
OK

A02047
ON
EGR
ONOFF
VSV is ON VSV is OFF
G
E11
Air
FG Air
F EE
DI±300
± DIAGNOSTICSENGINE (1MZ±FE)
535 Author: Date:
4 Check VSV for EGR.
PREPARATION:
(a) Remove the glove compartment (See page SF±73).
(b) Disconnect the E11 connector of ECM.
(c) Turn the ignition switch ON.
CHECK:
Check VSV function.
(1) Connect between terminal EGR of the ECM and
body ground (VSV is ON).
(2) Disconnect between terminal EGR of the ECM and
body ground (VSV is OFF).
OK:
(1) VSV is ON:
Air from pipe E flows out through pipe F.
(2) VSV is OFF:
Air from pipe E flows out through pipe G.
OK Go to step 7.
NG
5 Check operation of VSV for EGR (See page SF±56).
NG Replace VSV for EGR.
OK
Check for open in harness and connector
between engine room J/B and ECM
(See page IN±31).
6 Check EGR system (See page EC±11).
NG Repair or replace.
OK

S05410
Vacuum
EGR Valve
± DIAGNOSTICSENGINE (1MZ±FE)
DI±301
536 Author: Date:
7 Check EGR valve.
PREPARATION:
(a) Disconnect the vacuum hose from EGR valve.
(b) Start the engine.
CHECK:
Check whether the engine stall when apply vacuum to EGR
valve.
OK:
Engine runs rough or stall.
NG Repair or replace EGR valve.
OK
8 Check vacuum control valve (See page EC±11).
NG Replace vacuum control valve.
OK
Check and replace ECM (See page IN±31).

DI±302
± DIAGNOSTICSENGINE (1MZ±FE)
537 Author: Date:
DTC P0402 Exhaust Gas Recirculation Flow
Excessive Detected (Ex CA Spec.)
CIRCUIT DESCRIPTION
Refer to DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on page DI±292.
DTC No.DTC Detecting ConditionTrouble Area
P0402
When EGR cut±off, lift amount of EGR valve is
2.6 mm (0.1 in.) or more
(2 trip detection logic)

EGR valve stuck open

VSV for EGR open malfunction

Short in VSV circuit for EGR

Open or short in EGR valve position sensor circuit

EGR valve position sensor

ECM
See DTC P0401 (Exhaust Gas Recirculation Flow Insufficient Detected) on See page DI±292 for SYS-
TEM CHECK DRIVING PATTERN and WIRING DIAGRAM.
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.
TOYOTA hand±held tester
1 Check connection and blockage of vacuum hose.
NG Repair or replace vacuum hose.
OK
2 Check VSV for EGR (See page DI±292, step 5).
OK Go to step 4.
NG
DI07X±06

± DIAGNOSTICSENGINE (1MZ±FE)
DI±303
538 Author: Date:
3 Check operation of VSV for EGR (See page SF±56).
NG Replace VSV for EGR.
OK
Check for short in harness between VSV for
EGR and ECM (See page IN±31).
4 Check EGR valve (See page EC±11).
NG Repair or replace EGR valve.
OK
5 Check EGR valve position sensor (See page DI±358).
NG Repair or replace EGR valve position sensor or
harness.
OK
Check and replace ECM (See page IN±31).
OBDII scan tool (excluding TOYOTA hand±held tester)
1 Check connection and blockage of vacuum hose.
NG Repair or replace vacuum hose.
OK

DI±304
± DIAGNOSTICSENGINE (1MZ±FE)
539 Author: Date:
2 Check VSV for EGR (See page DI±292, step 5).
OK Go to step 4.
NG
3 Check operation of VSV for EGR (See page SF±56).
NG Replace VSV for EGR.
OK
Check for short in harness between VSV for
EGR and ECM (See page IN±31).
4 Check EGR valve (See page EC±11).
NG Repair or replace EGR valve.
OK
5 Check EGR valve position sensor (See page DI±358).
NG Repair or replace EGR valve position sensor or
harness.
OK
Check and replace ECM (See page IN±31).

FI7081
Waveform of Oxygen Sensor
before CatalystNormal Catalyst Waveform of Oxygen Sensor
after Catalyst
FI7132
Engine Speed
2,500 ~ 3,000 rpm
Idling
IG SW OFF(a)(b)(c) (d)
Time Warmed up 3 min. or so Check
± DIAGNOSTICSENGINE (1MZ±FE)
DI±305
540 Author: Date:
DTC P0420 Catalyst System Efficiency Below Threshold
(Except California Spec.)
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 the same
amplitude
(2 trip detection logic)

Three±way catalytic converter

Open or short in heated oxygen sensor circuit

Heated oxygen sensor
CONFIRMATION ENGINE RACING PATTERN
DI07Y±06

FI6514
OX Signal Waveform (Oscilloscope)
1 V
0 V
200 m sec./Division
DI±306
± DIAGNOSTICSENGINE (1MZ±FE)
541 Author: Date:
(a) Connect the TOYOTA hand±held tester to the DLC3, or connect the probe of the oscilloscope between
terminals OXR1, OXL1, OXS 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 waveform of the heated oxygen sensor, bank 1, 2 sensor 1 (OXR1, OXL1),
oscillate around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor,
bank 1 sensor 2 (OXS).
HINT:
If there is a malfunction in the system, the waveform of the
heated oxygen sensor, bank 1 sensor 2 (OXS), is almost the
same as that of the heated oxygen sensor, bank 1, 2 sensor 1
(OXR1, OXL1), 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
HINT:
Read freeze frame data using TOYOTA hand±held theater or OBD II scan tool. Because freeze frame re-
cords the engine conditions when the malfunction is detected, when troubleshooting it is useful for determin-
ing 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 (1MZ±FE)
DI±307
542 Author: Date:
3 Check heated oxygen sensor (bank 1, sensor 1) (See page DI±255).
NG Repair or replace.
OK
4 Check heated oxygen sensors (bank 1, 2 sensor 2) (See page DI±265).
NG Repair or replace.
OK
Replace three±way catalytic converter.

A01674
Waveform of
A/F Sensor
Normal CatalystWaveform of Heated Oxygen
Sensor Behind Catalyst
Abnormal Catalyst DI±308
± DIAGNOSTICSENGINE (1MZ±FE)
543 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 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.


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 flatteringly
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 sensors (bank 1, 2 sensor 1) circuit

A/F sensors (bank 1, 2 sensor 1)
DI1K4±03