O2 sensor TOYOTA CAMRY 2000 Service Repair Manual

46ENGINEÐ1MZ±FE ENGINE

MAJOR DIFFERNCES
Major differences between the new 1MZ±FE engne and previous engine are listed below.
Item
Outline
Cooling SystemAn aluminum radiator core is used for weight reduction.
Intake and Exhaust System
Through the optimized allocation of the exhaust pipe supports, the number
number of supports has been reduced from 5 to 4, thus reducing the noise
and vibration which are transmitted to the vehicle body.
Fuel SystemA fuel returnless system has been adopted to prevent the internal temperature
of the fuel tank from rising, and to reduce evaporative emissions.
Engine MountingThe characteristics of the engine mounts, torque rod, and absorber have been
optimized to reduce noise and vibration.
Engine Control System
A communication circuit has been provided between the ECM and the
ABS & TRAC ECU in conjunction with the adoption of the TRAC
(Traction Control) system.*
The fuel pressure control has been discontinued in conjunction with the
adoption of the fuel returnless system.
Instead of using the IDL signal input from the throttle position sensor,
the ECM now uses the VTA signal to detect the completely closed state of
the throttle valve.
A new EGR system which uses a EGR valve position sensor is used.
A communication method of the ECM and the hand±held tester has been
changed from the SAEJ1962 to the ISO 9141±2.
*: Applicable only to Vehicle Equipped with the TRAC System.

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


53ENGINEÐ1MZ±FE ENGINE
2) VCV (Vacuum Control Valve)
The VCV is a valve that regulates the intake manifold
vacuum that is appllied to the VSV to a constant level
(±17 kPa, ±130 mm Hg.)
The intake manifold vacuum that is supplied
through the S port is applied to the diaphragm. If this
force becomes greater than the spring force, the
diaphragm moves downward, allowing the valve to
close the S port and the atmosphere supplied
through the filter. Conversely, if the vacuum that is
applied to the diaphragm becomes weaker, the
diaphragm moves upward, causing the valve to
open and to shut off the atmosphere and supply the
intake manifold vacuum. This process is repeated to
regulate the vacuum in the Z port to a constant level.
3) EGR Valve Position Sensor
The EGR valve position sensor is mounted on the EGR valve. This sensor converts the EGR valve opening into a
voltage and sends it to the ECM as the EGR valve position signal.

54ENGINEÐ1MZ±FE ENGINE
Operation
The ECM executes duty control of the VSV to control the vacuum that has been regulated to a constant level by the
VCV, thus controlling the vacuum that is applied to the EGR valve.
Also, the EGR valve position sensor in the EGR valve detects the EGR valve opeining to provide feed back control
to the ECM, thus achieveing a target opining that is appropriate for the engine condition.
7. Others
A communication circuit has been provided between the ECM and the ABS & TRAC ECU in conjunction with the
adoption of the TRAC (Traction Control) system. The ECM sends signals such as the throttle position signal and the
engine speed signal to the ABS & TRAC ECU. In addition, the ECM executes fuel cutoff in accordance with the
request signals from the ABS & TRAC ECU.

72CHASSISÐBRAKES
5. Function of Components
No.ComponentFunction
1Slip Indicator LightBlinks to inform the driver when the TRAC system is operated.
2TRAC OFF Indicator Light
Lights to inform the driver when the TRAC system is turned OFF by
the by the TRAC OFF switch. And, blinks to alert the driver when
the ECU detects the malfunction in the TRAC system.
3ECM
Sends signals to the ABS & TRAC ECU, such as the throttle
valve opening angle, specific volume of intake air signal, etc.
Controls the engine output and shift timing in accordance with
the fuel cutoff request and shift timing request that are output by
the ABS & TRAC ECU.
4ABS & TRAC ECU
Judges the vehicle driving condition based on signals from 4 speed
sensors and signals from ECM, and sends fuel cut and shift timing
demand signals to the ECM and brake control signal to the ABS &
TRAC actuator.
5ABS & TRAC Actuator
Controls the brake fluid pressure to each brake wheel cylinder
of the driving wheel (front wheel) by signals from the ABS &
TRAC ECU.
ABS & TRAC
Solenoid RelayDirects electricity to the solenoid valves in the actuator.
6ABS & TRAC
RelayPump Motor
RelayControls the pump motor operation in the actuator.
7Speed Sensors (Front and Rear)Detect the wheel speed of each of four wheels.
8Throttle Position SensorDetects the throttle valve opening angle.
9TRAC OFF SwitchTurns the TRAC system inoperative.

80 CHASSISÐBRAKES
ABS & TRAC ECU
1) Wheel Speed Control
The ABS & TRAC ECU constantly receives signals from 4 speed sensors and calculates the speed of each wheel and
vehicle speed.
During sudden acceleration or driving on a slippery surface, if the drive wheels (front wheels) start to slip, the
difference in speed between the drive wheels are slipping.
Then, the ABS & TRAC ECU executes the right and left independent control of the front wheel brakes, the engine
torque control through fuel cutoff, and shift timing control according to the extent of the slip.
TRAC operation processes are described below.
1. The vehicle speed is determined by way of the rear wheel speed. This speed is then compared to the speed of the
front wheels, which are the drive wheels, to determine the slip condition of the drive wheels (front wheels).
2. The target control speed for the drive wheels is set based on the estimated vehicle speed.
3. If the speed of the front wheels, which are the drive wheels, exceeds the control starting speed, the ABS & TRAC
ECU determines that a slip has occurred and cuts off fuel according to the number of cylinders. By executing
engine torque control and brake control in this manner, the system regulates the speed
so that front wheels attain the target control speed. In addition, the system executes control to
prohibit the shifting of the automatic transaxle at this
time.
4. TRAC control ends when the drive wheels move to non±slippery surface or when the driver releases the
accelerator pedal.

104BODY ELECTRICALÐAIR CONDITIONING
3. Defroster Nozzle
The front defroster nozzle inner wall is modified into a radial configuration for a smoother air flow and improved
defroster performance.
4. Air Conditioning Amplifier
On the new Camry, the air conditioning amplifier that is provided on the 1MZ±FE engine model is an individual
amplifier unit type and on the 5S±FE engine model is a type that is integrated with the ECM.
The air conditioning amplifier controls the air conditioning system in accordance with the signals received from
sensors, switches, etc.
Function
Details
Magnetic Clutch Relay Control
When the blower switch and the air conditioning switch are turned on to-
gether, or when the air outlet mode is switched to defroster, the magnetic
clutch relay turns on and activates the compressor.
When one of the following conditions is met while the compressor is
turned on, the magnetic clutch relay is turned off and stops the compres-
sor:
i) The air temperature immediately after passing through the evaporator
is detected to be below 3C (37.4F) by the thermistor.
ii) The compressor speed detected by the lock sensor is compared with
the engine speed signal, and the compressor's slip rate exceeds a pre-
determined level (compressor locked).
iii) ªAir conditioner cutº was requested by the ECM to maintain engine
performance or idling speed.
Compressor Delay ControlWhen the air conditioning switch is turned on, the engagement of the mag-
netic clutch is delayed.
Air Conditioning Indicator Light
Control
When the blower switch and the air conditioning switch are turned on to-
gether, or when the air outlet mode is switched to defroster, and the com-
pressor is activated, the indicator lamp of the air conditioning switch is
turned on.
If compressure lock occurs during compressor operation, the indicator
lamp flashes every 1 second.

106BODY ELECTRICALÐACCESSORIES
SystemOutline
SRS Airbag
The SRS (Supplemental Restraint System) airbag is provided for the driver
and front passenger. The SRS airbag has been designed to lessen the shock to
the head and chest of the driver and front passenger in the event of a frontal
impact collision as a supplement to the seat belt.
A 1±sensor type airbag system is used in which the detection of decelera-
tion during a collision as well as control of the airbag system is accom-
plished by the airbag sensor assembly.
The basic construction and operation are the same as in the '96 Avalon.
However, the inflator for front passsenger and airbag sensor assembly have
been changed.
For details, see page 111.
Cruise Control System
Once it has been set at a desired vehicle speed, this system automatically
adjusts the engine throttle position to maintain the vehicle speed at the de-
sired speed without operating the acceleration pedal.
The basic construction and operation are the same as in the previous model.
However, in the new model, a new type acutator has been adopted. Also, the
functions of the cruise control ECU has been changed. For details, see page
116.
Moon Roof
The moon roof is a tilt±up and sliding type the same as in the previous mod-
el. This system includes ªkey±off operationº, which is the same as with the
power window system. The new model offers an additional ªone±touch slide
openº function which enables the moon roof to fully open when the slide
switch is pressed toward the opening side for a few seconds.
Electrical Remote Control Mirror
The electrical remote control mirrors used in the previous model are also
used in the new model. Also, the internal heater to remove water drops from
the mirror surface is provided.
Key Reminder System
When the driver's door is opened with the ignition key in the ACC or LOCK
position, this system sounds a buzzer to warn the driver that the ignition key
has not been removed.
The basic construction and operation are the same as in the previous model.

111 BODY ELECTRICALÐACCESSORIES
 SRS AIRBAG
1. General
The SRS (Supplemental Restraint System) airbag is designed to help lessening the shock to the driver and front
passenger as a supplement to the seat belt. In a collision, the aribag sensor detects the shock and if the front±to±rear
shock is greater than a specified value, the airbags stored in the steering wheel pad for the driver and above the glove
box for the front passenger inflate instantly to help reducing the likelihood of the driver's or front passenger's head
and chest directly hitting the steering wheel or instrument panel.
As in the '96 Avalon, a 1±sensor type airbag system is used, in chich the detection of deceleration during a collision
is accomplished by the airbag sensor enclosed in the airbag snesor assembly.
The airbag system is controlled by the airbag sensor assembly. It has a self±diagnosis function. When it detects a
system malfunction, it lights up the SRS warning light on the combination meter to alert the driver.
The basic construction and operation are the same as in teh '96 Avalon. However, 2 types of the inflator for front
passenger have been adopted in the new Camry: TRW made and Morton made. Also, the construction of airbag sensor
assembly has been changed.

System Diagram
The activation processes of the SRS airbag is as illustrated below.

113 BODY ELECTRICALÐACCESSORIES
4. construction and Operation
Inflator and Bag for Front Passenger
1) General
The inflator and ag for front passenger are inserted inside the case, and located in the passenger side instrument panel.
the bag is made of strong nylon cloth, and becomes inflated by the argon gas flowed from the inflator. Also, 2 types
of the inflator for front passenger have been adopted: TRW made and Morton made.
2) Inflator of TRW Made
The inflator of TRW made is comprised of a squib, propellant grain, burst cup and high pressure argon gas.
If the airbag sensor is turned on by deceleration due to frontal collision, electric current then ignites the squib located
in the inflator. the frame of squib spreads instaneously to the propellant grain. If the internal pressure of the burst cup
increases by the combustion of the propellant grain, the burst cup will be released by making its bulkhead break. With
this, the gas which expanded by the tgeat of the ignition of the propellant grain flows into the airbag via the diffuser,
thus inflating the airbag.

Construction