brakes TOYOTA CAMRY 2000 Service Owner's Manual

76CHASSISÐBRAKES
b. During Vehicle Acceleration (TRAC System Activated)
When a front wheel slips during acceleration, the TRAC system controls the engine output and braking of the front
wheels to help preventing wheel slippage.
The brake fluid pressure applied to the right and left front wheels is controlled separately accordingly to 3 control
modes ( pressure increase, holding, and pressure reduction) as explained below.
i) Pressure Increase Mode
During sudden acceleration or driving on a slippery surface, if the front wheels start to slip, a control signal from the
ABS & TRAC ECU causes the ABS & TRAC actuator to control the valves and pumps as described below, to effect
the pressure increase mode.
When the master cut and reservoir cut solenoid valves turn ON, port B is closed, port H is open and the pump operates
at the same time.
Accordingly, the brake fluid will be suctioned up from the master cylinder through parts G and H.
Then the brake fluid that is pressurized by the pump will be applied to the wheel cylinder through C and D.
Also, the brake fluid that pressurized by the pump is regulated to a constant pressure by the pressure regulator valve.

Hydraulic Circuit

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS & TRAC ECUOperation
Master Cut Solenoid ValveONPort BClosed
Reservoir Cut Solenoid ValveONPort HOpen
Pressure Holding ValveOFFPort COpen

78 CHASSISÐBRAKES
ii) Pressure Holding Mode
When the fluid pressure in the wheel cylinder is increased or decreased to attain the required pressure, the ABS &
TRAC ECU sends a control signal to turn ON the pressure holding valve.
Then, the fluid pressure that is applied to the wheel cylinder is cut off to hold the fluid pressure in the wheel cylinder.

Hydraulic Circuit

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS & TRAC ECUOperation
Master Cut Solenoid ValveONPort BClosed
Reservoir Cut Solenoid ValveOFFPort HClosed
Pressure Holding ValveONPort CClosed
Pressure Reduction ValveOFFPort FClosed
PumpONRotating

79CHASSISÐBRAKES
iii) Pressure Reduction Mode
When the fluid pressure in the wheel cylinder needs to be decreased, the ABS & TRAC ECU sends a control signal
to turn the pressure reduction valve ON, causing port F to open
Accordingly, the brake fluid in the wheel cylinder flows to ports E and F, reservoir, and pump, to reduce the fluid
pressure in the wheel cylinder.
The fluid pressure reduction rate is controlled by repetition of the pressure reduction and holding mode.

Hydraulic Circuit

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS & TRAC ECUOperation
Master Cut Solenoid ValveONPort BClosed
Reservoir Cut Solenoid ValveOFFPort HClosed
Pressure Holding ValveONPort CClosed
Pressure Reduction ValveONPort FOpen
PumpONRotating

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.

81CHASSISÐBRAKES
2) Initial Check
An initial check is carried out once every a few seconds after the ignition was turned on. The functions of each
solenoid valve and pump motor in the actuator are checked on order.
3) Self±Diagnosis
If the ABS & TRAC ECU detects a malfunction in the engine, ABS or TRAC system, it blinks the TRAC OFF
indicator light to alert the driver of the malfunction. At the same, the ABS & TRAC 1997 Avalon Repair Manual
(Pub. No. RM504U) for the diagnostic code check method, diagnostic code and diagnostic code clearance.
4) Fail±Safe
In the event of a malfunction in the engine, ABS or TRAC system, the ABS & ECU prohibits the TRAC system.
Thus, the brake and engine controls will operate in the same conditions as those without the TRAC system.

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(f) Stop and check.
(g) Take vehicle to
Toyota dealer
immediately.
(h) Close all doors.
(i) Replace bulb.
(j) Take vehicle to
Toyota dealer
immediately. (type A)
(type B)
If the indicator or
buzzer comes on...Do this.
(k) Add washer fluid.
(l) Take vehicle to
Toyota dealer.
(m) Remove key.Key reminder
buzzer
If the indicator or
buzzer comes on...Do this.(a) Brake System Warning Light
This light has the following functions:
Parking brake reminder
If this light is on, make sure the parking
brake is fully released. The light should
go off.
Low brake fluid level warning
If this light comes on and stays on while
you are driving, slow down and pull off
the road. Then stop the vehicle carefully.
Remember that stopping distance and ped-
al effort may be increased. There may be
a problem somewhere in the brake sys-
tem. Check the fluid level of the see±
through reservoir.
To make sure the parking brake has not
caused the warning light to come on,
check to see that the parking brake is
fully released.
If the brake fluid level is low...
At a safe place, test your brakes by start-
ing and stopping.

If you judge that the brakes still work
adequately, drive cautiously to your
nearest dealer or shop for repairs.

If the brakes are not working, have the
vehicle towed in for repairs. (For tow-
ing information, see Part 4.)

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The cup holder is designed for holding
cups or drink±cans securely in its
holes.
Front: To use the holder, open the lid.
Rear: To use the holder, pull it out.
CAUTION

Do not place anything else other
than cups or drink±cans on the cup
holder, as such item may be thrown
about in the compartment and poss-
ibly injure people in the vehicle
during sudden braking or an acci-
dent.

To reduce the chance of injury in
case of an accident or sudden stop
while driving, keep the cup holder
closed when it is not in use.
Traction control system
Slip indicator light
ºTRAC OFFº indicator/warning light
AUTOMATIC TRACTION CONTROL SYS-
TEM
The traction control system automatical-
ly helps control the spinning of the
front wheels which may occur when ac-
celerating on slippery road surfaces,
thus assisting driver to control the driv-
ing power of the front wheels. When
you turn the ignition switch on, the
traction control system always turns on
automatically, and the slip indicator
light and ºTRAC OFFº indicator/warning
light will come on. The indicator lights
will go off after about 3 seconds.
Leave the system on during ordinary
driving so that it can operate when
needed. When traction control is ap-
plied, the slip indicator light blinks.
You may hear a sound in the engine
compartment for a few seconds when the
engine is started or just after the vehicle
is started. This means that the traction
control system is in the self±check mode,
and does not indicate malfunction. When
the traction control system is operating,
you may feel vibration or noise of your
vehicle, caused by operation of the
brakes. This indicates the system is func-
tioning properly.

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Your engine is fitted with twin ground
electrode platinum±tipped spark plugs.
NOTICE
Use only twin ground electrode plati-
num±tipped spark plugs for your en-
gine performance.
Brake system
TANDEM MASTER CYLINDER BRAKE
SYSTEM
The tandem master cylinder brake system
is a hydraulic system with two separate
sub±systems. If either sub±system should
fail, the other will still work. However, the
pedal will be harder to press, and your
stopping distance will be longer. Also, the
brake system warning light may come on.
CAUTION
Do not drive your vehicle with only a
single brake system. Have your
brakes fixed immediately.
BRAKE BOOSTER
The brake booster uses engine vacuum to
power±assist the brakes. If the engine
should quit while you are driving, you can
bring the vehicle to a stop with normal
pedal pressure. There is enough reserve
vacuum for one or two stopsÐbut no
more!
CAUTION

Do not pump the brake pedal if the
engine stalls. Each push on the
pedal uses up your vacuum reserve.

Even if the power assist is com-
pletely lost, the brakes will still
work. But you will have to push the
pedal hardÐmuch harder than nor-
mal. And your braking distance will
be longer.
ANTI±LOCK BRAKE SYSTEM (with
ºABSº warning light)
The anti±lock brake system is designed to
automatically help prevent lock±up of the
wheels during sudden braking or braking
on slippery road surfaces. This assists in
providing directional stability and steering
performance of the vehicle under these
circumstances.
The anti±lock brake system becomes op-
erative after the vehicle has accelerated
to a speed in excess of approximately 10
km/h (6 mph). It stops operating when the
vehicle decelerate to a speed below
approximately 5 km/h (3 mph).
Twin ground electrode
platinum±tipped spark plugs

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Even if the anti±lock brake system should
fail, the brake system will still operate
conventionally. However, when the ºABSº
warning light is on (and the brake system
warning light is off), the anti±lock brake
system is not assisting brake performance
so that the wheels can lock±up during
sudden braking or braking on slippery
road surfaces. Have your vehicle checked
by your Toyota dealer as soon as pos-
sible.
DRUM±IN±DISC TYPE PARKING BRAKE
SYSTEM (1MZ±FE engine)
Your vehicle has a drum±in±disc type
parking brake system. This type of brake
system needs bedding±down of the brake
shoes periodically or whenever the parking
brake shoes and/or drums are replaced.
Have your Toyota dealer perform the bed-
ding±down.
Brake pad wear limit indicators
The brake pad wear limit indicators on
your disc brakes give a warning noise
when the brake pads are worn to where
replacement is required.
If you hear a squealing or scraping noise
while driving, have the brake pads
checked and replaced by your Toyota
dealer as soon as possible. Expensive ro-
tor damage can result if the pads are not
replaced when necessary.
Luggage stowage precautions
When stowing luggage or cargo in the
vehicle, observe the following:

Put luggage or cargo in the trunk when
at all possible. Be sure all items are
secured in place.

Be careful to keep the vehicle bal-
anced. Locating the weight as far for-
ward as possible helps maintain bal-
ance.

For better fuel economy, do not carry
unneeded weight.
CAUTION

To prevent luggage or packages
from sliding forward during braking,
do not stack anything in the en-
larged trunk. Keep luggage or pack-
ages low, as close to the floor as
possible.

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(b) Starting the engine
Before starting the engine, be sure to fol-
low the instructions in º(a) Before crank-
ingº.
Normal starting procedure
The multiport fuel injection system/sequen-
tial multiport fuel injection system in your
engine automatically controls the proper
air±fuel mixture for starting. You can start
a cold or hot engine as follows:
1. With your foot off the accelerator ped-
al, crank the engine by turning the key
to ºSTARTº. Release it when the en-
gine starts.
2. After the engine runs for about 10 se-
conds, you are ready to drive.
If the weather is below freezing, let the
engine warm up for a few minutes before
driving.
If the engine stalls...
Simply restart it, using the correct proce-
dure given in normal starting.
If the engine will not start...
See ºIf your vehicle will not startº in Part
4.NOTICE
Do not crank for more than 30 se-
conds at a time. This may overheat
the starter and wiring systems.
Do not race a cold engine.
If the engine becomes difficult to
start or stalls frequently, have the
engine checked immediately.

Always slow down in gusty crosswinds.
This will allow you much better control.

Drive slowly onto curbs and, if pos-
sible, at a right angle. Avoid driving
onto high, sharp±edged objects and
other road hazards. Failure to do so
can lead to severe tire damage result-
ing in tire bursts.

When parking on a hill, turn the front
wheels until they touch the curb so
that the vehicle will not roll. Apply the
parking brake, and place the transmis-
sion in ºPº (automatic) or in first or
reverse (manual). If necessary, block
the wheels.

Washing your vehicle or driving through
deep water may get the brakes wet. To
see whether they are wet, check that
there is no traffic near you, and then
press the pedal lightly. If you do not
feel a normal braking force, the brakes
are probably wet. To dry them, drive
the vehicle cautiously while lightly
pressing the brake pedal with the park-
ing brake pulled. If they still do not
work safely, pull to the side of the road
and call a Toyota dealer for assistance.
Tips for driving in various
conditions