oxygen sensors TOYOTA CAMRY 2000 Service User Guide

48ENGINEÐ1MZ±FE ENGINE

ENGINE CONTROL SYSTEM
1. General
The engine control system of the new 1MZ±FE engine is basically the same in construction and operation as that of
the previous 1MZ±FE engine. However, the fuel pressure control has been discontinued and the EGR control system
has been changed.
The engine control system of the new 1MZ±FE engine and previous 1MZ±FE engine are compared below.
System
OutlineNewPrevious
SFI
(SequentialA L±type SFI system directly detects intake air mass with
a hot wire type mass air flow meter.(q
Multiport Fuel
Injection)The fuel injection system is a sequential multiport fuel
injection system.
ESA
Ignition Timing is determined by the ECM based on
signals from various sensors. The ECM corrects ignition
timing in response to engine knocking.

(Electronic Spark2 knock sensors are used to improve knock detection.(p
Advance)In vehicles equipped with automatic transaxle, torque
control correction during gear shifting has been used to
minimize the shift shock.

IACA rotary solenoid type IAC valve controls the fast idle(Idle Air Control)
A rotary solenoid type IAC valve controls the fast idle
and idle speeds.
ACIS
(Acoustic Control
The intake air passages are switched according to the en-
gine speed and throttle valve angle to increase perfor(Acoustic Control
Induction System)
gine speed and throttle valve angle to increase perfor-
mance in all speed ranges.
Fuel Pressure
ControlIn hot engine conditions, the fuel pressure is increased to
improve restartability.
Oxygen Sensor
Heater ControlMaintains the temperature of the oxygen sensor at an
approppiate level to increase accuracy of detection of
the oxygen concentration in the exhaust gas.

EGR Cut±Off
ControlCuts off EGR according to the engine condition to
maintain drivability of the vehicle and durability of
EGR components.
Ð
EGR Control
Uses the duty control type VSV and EGR valve position
sensor, controlling the EGR volumne in accordance with
engine conditions.
Ð
Evaporative
Emission ControlThe ECM controls the purge flow of evaporative emis-
sions (HC) in the charcoal canister in accordance with
engine conditions.

Diagnosis
When the ECM detects a malfunction, the ECM diagnoses
and memorizes the failed section.
DiagnosisThe diagnosis system includes a function that detects a
malfunction in the evaporative control system.Ð
Fail SafeWhen the ECM detects a malfunction, the ECM stops
or controls the engine according to the data already stored
in memory


CAMRY ± NEW FEATURES
No.2 INJECTOR
SENSORS ACTUATORS
VG
RSO IGF NE
ECM
IGTI

IGT3
#10
G22
THW
THA
VTA1
STA
SPD
AFR
AFL
OXS
EGLS
THG
KNKR
CF
NSW
A/C
ACIS
FC
ACT
MAFR
HAFL
HREL
#20
#30
#40
#50
#60
MASS AIR FLOW METER
R, 2, L KNKLIGSW
RSC
CRANKSHAFT POSITION SENSOR
Engine Speed Signal
Crankshaft Angle Signal
CAMSHAFT POSITION SENSOR
Crankshaft Angle Signal
ENGINE COOLANT TEMP.
SENSOR
INTAKE AIR TEMP. SENSOR
THROTTLE POSITION SENSOR
Throttle Position Signal
IGNITION SWITCH
Starting Signal
Ignition Signal
VEHICLE SPEED SENSOR
COMBINATION METER
AIR-FUEL RATIO SENSOR
(Bank 1, Sensor 1)
AIR-FUEL RATIO SENSOR
(Bank 2, Sensor 1)
HEATED OXYGEN SENSOR
(Bank 1, Sensor 2)
EGR VALVE POSITION SENSOR
EGR GAS TEMP. SENSOR
KNOCK SENSORS
PARK / NEUTRAL POSITION
SWITCH
Neutral Start Signal
AIR CONDITIONING AMPLIFIER
A / C Switch Signal
COOLING FAN RELAYNo.1 INJECTOR
No.3 INJECTOR
No.4 INJECTOR
No.5 INJECTOR
No.6 INJECTOR
ESA
IGNITER
IGNITION COILS
SPARK PLUGS
IAC
CONTROL VALVE
ACIS
VSV
FUEL PUMP CONTROL
CIRCUIT OPENING RELAY
AIR CONDITIONING CONTROL
AIR CONDITIONING
AMPLIFIER
AIR FUEL RATIO SENSOR
HEATER CONTROL
AIR FUEL RATIO SENSOR
HEATER RELAY
AIR FUEL RATIO SENSOR
HEATER (Bank 1, Sensor 1)
AIR FUEL RATIO SENSOR
HEATER (Bank 1, Sensor 2)SFI
(Continued)
KNOCK SENSORS
11
Construction
1) California Specification Automatic Transaxle Model
The configuration of the engine control system in the 1MZ-FE engine of the '98 Camry is as shown in
the following chart. Shaded portions
differ from the 1MZ-FE engine of the '97 Camry.

CAMRY ± NEW FEATURES
150EG01
Circuit Opening RelayIgnition
SwitchEFI
Main
Relay
DLC1 Pressure
RegulatorVehicle Speed
SensorPark / Neutral Position Switch*
Fuel Pump
BatteryMIL
Air
Conditioning
Amplifier
DLC3
Stop Light Switch
Electrical Load Switch
Air-Fuel Ratio Sensor Heater Relay
ECM Fuel
Filter
Pulsation
DamperVSV
(for EVAP)Vapor
Pressure
Sensor
VSV
for Vapor
Pressure
Sensor
Charcoal CanisterVCV
Intake Air Temp.
SensorIAC Valve
VSV (for EGR)
Mass Air Flow
Meter
Air-Fuel Ratio Sensor
(Bank 1, Sensor 1)Throttle
Position
Sensor
Actuator
DIS
Injector
VSV (for ACIS)
EGR
Valve
Position
Sensor
EGR
Valve EGR Gas
Temp. Sensor Camshaft
Position
Sensor
Engine Coolant
Temp. SensorWU-TWC
WU-TWC
Crankshaft
Position SensorKnock Sensors
Air-Fuel Ratio Sensor
(Bank 2, Sensor 1)Heated Oxygen Sensor
(Bank 1, Sensor 2)
13
Engine Control System Diagram
1) California Specification Automatic Transaxle Model
*: Only for the Automatic Transaxle Models

NF
NEW FEATURES Ð 5S-FNE ENGINE19
ENGINE CONTROL SYSTEM
1. General
An engine control system based on the 5S-FE engine has been adopted. The knock sensor has been discontin-
ued because natural gas has a high octane value and is less susceptible to knocking.
The engine control system of 5S-FNE and 5S-FE engines are compared below.
System
Outline5S-FNE5S-FE
SFI
Sequential
A D-type SFI system is used, which indirectly detects
intake air volume by manifold absolute pressure sensor.
Sequential
Multiport Fuel
Injection
The fuel injection system is a sequential multiport fuel
injection system.
Ignition timing is determined by the ECM based on sig-
nals from various sensors.
ESA
Electronic Spark
AdvanceThe ECM corrects the ignition timing in response to en-
gine knocking in accordance with the signals received
from the knock sensor.
Ð
Advance
Torque control correction during gear shifting had been
used to minimize the shift shock.*1
IAC
(Idle Air Control)A rotary solenoid type IAC valve controls the fast idle
and idle speeds.
(1-Coil Type
Built-in Driver)(2-Coil Type)
Fuel Pump ControlFuel pump operation is controlled by signal from the
ECM.Ð
Fuel Cut-Off
Control
The fuel shutoff valves for the fuel tank, fuel pressure
regulator, and delivery pipe are shut off to stop the sup-
ply of fuel when the ignition switch is turned OFF or
during abnormal conditions (such as engine stalling,
SRS airbag deployed, etc.).
Ð
Oxygen Sensor
and Air Fuel Ratio
Sensor
Heater ControlMaintains the temperature of the oxygen sensor and air
fuel ratio sensor at an appropriate level to increase accu-
racy of detection of the oxygen concentration in the ex-
haust gas.
*2
EGR Cut-Off
ControlCuts off EGR according to the engine condition to
maintain drivability of the vehicle and durability of the
EGR components.

Evaporative
Emission ControlThe ECM controls the purge flow of evaporative emis-
sions (HC) in the charcoal canister in accordance with
engine conditions.
Ð
Air Conditioning
Cut-Off ControlBy turning the air conditioning compressor ON or OFF
in accordance with the engine condition, drivability is
maintained.
*3*3
When the ECM detects a malfunction, the ECM diag-
noses and memorized the failed section.
DiagnosisThe diagnosis system includes a function that detects a
malfunction in the evaporative emission control sys-
tem.
Ð
Fail-Safe
When the ECM detects a malfunction, the ECM stops
or controls the engine according to the data already
stored in memory.

*1: Only for Automatic Transaxle Model
*
2: Air fuel ratio sensor only for California specification model.
*
3: The air conditioning magnet clutch controled by the ECM

NEW FEATURES Ð 5S-FNE ENGINE
(Continued)
PIM
NE
G
THW
THA
VTA
AF
#10+
#20
#30
#40
IGT1,
IGT2
IGF
RSD
EGR
OX2
HTAF
HT2
MGC
FUEL W
PSW
ELS
NSW
F/PS
A/C SW
ECM
STA
SPD
R,2,L
STP
#40+ #30+ #20+ #10
FUEL
20
2. Construction
The configuration of the engine control system in the 5S-FNE engine is as shown in the following chart.
SENSORS
MANIFOLD ABSOLUTE
PRESSURE SENSOR
CRANKSHAFT POSITION
SENSOR
CAMSHAFT POSITION
SENSOR
ENGINE COOLANT TEMP.
SENSOR
INTAKE AIR TEMP. SENSOR
THROTTLE POSITION SENSOR
IGNITION SWITCH
COMBINATION METER
wVehicle Speed Signal
AIR FUEL RATIO SENSOR
(Bank 1, Sensor 1)
HEATED OXYGEN SENSOR
(Bank 1, Sensor 2)
POWER STEERING OIL
PRESSER SWITCH
TAILLIGHT & REAR WINDOW
DEFOGGER SYSTEM
PARK/NEUTRAL POSITION
SWITCH
STOP LIGHT SWITCH
AIR CONDITIONING SWITCH
AIRBAG SENSOR ASSEMBLY
wFuel Cut-Off Signal
ACTUATORS
SFI
No. 1 INJECTOR
No. 2 INJECTOR
No. 3 INJECTOR
No. 4 INJECTOR
ESA
IGNITERS and
IGNITION COILS
SPARK PLUGS
IAC
CONTROL VALVE
EGR
VSV
AIR FUEL RATIO SENSOR
HEATER CONTROL
AIR FUEL RATIO SENSOR
HEATER
OXYGEN SENSOR HEATER
CONTROL
HEATED OXYGEN SENSOR
HEATER
AIRE CONDITIONING
CUT-OFF CONTROL
MAGNET CLUTCH RERAY
FUEL GAGE
LOW FUEL LEVEL WARNING
LIGHT

P21242 FI7210
A00027
Atmosphere
Flange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater
Coating (Ceramic)
Exhaust GasCoverIdeal Air±Fuel Mixture
Output Voltage
Richer ± Air Fuel Ratio ± Leaner
± DIAGNOSTICSENGINE (5S±FE)
DI±61
296 Author: Date:
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control (Except California Spec.)
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three±way
catalytic converter is used, but for the most efficient use of the three±way catalytic converter, the air±fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The heated oxygen sensor has the characteristic where by its output voltage changes suddenly in the vicinity
of the stoichiometric air±fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and
provide feedback to the computer for control of the air±fuel ratio.
When the air±fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the heated
oxygen sensor informs the ECM of the LEAN condition (small electromotive force: 0 V).
When the air±fuel ratio is RICHER than the stoichiometric air±fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the heated oxygen sensor informs the ECM of the RICH condition (large electromo-
tive force: 1 V).
The ECM judges by the electromotive force from the heated oxygen sensor whether the air±fuel ratio is RICH
or LEAN and controls the injection time accordingly. However, if malfunction of the heated oxygen sensor
causes output of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio control.
The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by
the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the
heater to heat the sensor for accurate oxygen concentration detection.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After engine is warmed up, heated oxygen sensor (bank 1
sensor 1) output does not indicate RICH even once when
conditions (a), (b) and (c) continue for at least 1.5 min.:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 ~ 100 km/h (25 ~ 62 mph)
(c) Throttle valve does not fully closed

Fuel system

Injector

Ignition system

Gas leakage on exhaust system

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

Heated oxygen sensor (bank 1 sensor 1)

ECM
DI00T±05

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

P21242 FI7210
A00027
Atmosphere
CoverIdeal Air±Fuel Mixture
Air Fuel Ratio
RicherLeaner
Exhaust GasFlange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platium Electrode
Heater
Coating(Ceramic)
Output Voltage
DI±244
± DIAGNOSTICSENGINE (1MZ±FE)
479 Author: Date:
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control (Except California Spec.)
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three±way
catalytic converter is used, but for the most efficient use of the three±way catalytic converter, the air±fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the
stoichiometric air±fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust
gas and provide feedback to the computer for control of the air±fuel ratio.
When the air±fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V).
When the air±fuel ratio is RICHER than the stoichiometric air±fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: > 0.45 V). The ECM judges by the electromotive force from the oxygen sensor whether the air±fuel
ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sen-
sor causes output of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio con-
trol.
The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by
the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the
heater to heat the sensor for accurate oxygen concentration detection.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After engine is warmed up, heated oxygen sensor (bank 1, 2
sensor 1) output does not indicate RICH ( 0.45 V ) even
once when conditions (a), (b), (c) and (d) continue for at least
2 min.:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40
SPD and 100 km/h (25
SPD and
62 mph)
(c) Throttle valve does not fully closed
(d) 140 sec. or more after starting engine
Fuel system

Injector

Ignition system

Gas leakage on exhaust system

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

Heated oxygen sensors (bank 1, 2 sensor 1)

ECM
DI07M±08

A07444
BatteryJunction Connector
MREL
ECM
B
B+
E1
E03
E03
E1E1
E03 OXL1
HTL1
OXR1
HTR
OXS
HTS
E8E8 E10 E11E7
E10
E10
E108
12
4
11
30
3
8
9
Y±R
3
2
4
1
W
BR
L±B
B
BR
3 2
4
1
B±Y
B±Y
B±Y
A A B Junction Connector
B
J28 J27
J27 B±YJunction Connector
2K
2J
3
1
2
5
EFI
2C 2A 1 5
F6
F4 1
1
B
W±B
EB
FL
MAINFusible
Link
Block
E03
Engine
Room
J/B
B±G
Heated Oxygen
Sensor
(Bank 1 Sensor 2)3
2
1
EDEC
P±BA
A
BR
BR4 B±YHeated Oxygen
Sensor
(Bank 1 Sensor 1)II3 B±WAC
J36 J35B±W
EFI Relay
BR
BR
2 7B±Y9
Heated Oxygen
Sensor
(Bank 2 Sensor 1)
D
± DIAGNOSTICSENGINE (1MZ±FE)
DI±245
480 Author: Date:
HINT:
After confirming DTC P0125, use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage output
of the heated oxygen sensors (bank 1, 2 sensor 1) from CURRENT DATA.
If voltage output of the heated oxygen sensors (bank 1, 2 sensor 1) is less than 0.1 V, heated oxygen sensors
(bank 1, 2 sensor 1) circuit may be open or short.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If the vehicle run out fuel, the air±fuel ratio is LEAN and DTC P0125 will be recorded.
The MIL then comes on.

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.

DI±246
± DIAGNOSTICSENGINE (1MZ±FE)
481 Author: Date:
1 Are there any other codes (besides DTC P0125) being output ?
YES Go to relevant DTC chart.
NO
2 Connect OBD II scan tool or TOYOTA hand±held tester, and read value for
voltage output of heated oxygen sensors (bank 1, 2 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand±held tester to the DLC3.
(b) Warm up the engine to normal operating temp.(above 75°C (169°F)).
CHECK:
Read voltage output of the heated oxygen sensors (bank 1,2 sensor 1) when engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 times using accelerator pedal.
OK:
Heated oxygen sensors (bank 1, 2 sensor 1) output a RICH signal
(0.45 V or more) at least once.
OK Go to step 10.
NG
3 Check for open and short in harness and connector between ECM and heated
oxygen sensors (bank 1, 2 sensor 1) (See page IN±31).
NG Repair or replace harness or connector.
OK