2000 TOYOTA CAMRY ECU

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.

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.

62CHASSISÐBRAKES
 MASTER CYLINDER
As in the previous model, the lockheed and
lockheed type master cylinder is used on the models
without ABS, and the portless and lockheed type
master cylinder is used on the models with ABS.
The portless and portless type master cylinder is
used on the models with ABS & TRAC system.
 ABS
1. General
As in the previous model, the braking of each wheel is controlled by the following 3 modes: pressure reduction,
pressure holding, and pressure holding mode.
During ABS activation, the ECU controls the fluid pressure of each front left and right wheels independently while
the fluid pressure of rear left and right wheels is controlled simultaneously.
However, the ABS actuator has been changed as shown in the table below. In addition, the diagnostic codes have
alsom been changed.
For diagnostic code check method, diagnostic code and diagnostic code clearance, see the 1997 Camry Repair
Manual (Pub. No. RM503U).
The operation of the ABS is the same as that of the '96 Corolla.

Type of ABS Actuator
Model
NewPreviousTypeNewPrevious
NIPPONDENSO ABS
(TMC Produced Model) 2±Position Solenoid Valve Type
Actuator
The ECU and realy are separate.3±Position Solenoid Valve Type
Actuato
The ECU and relay are separate.
BOSCH ABS
(TMM Produced Model)2±Position Solenoid Valve Type
Actuator with ECU and Relay3±Position Solenoid Valve and
Mechanical Valve Type Actuator
with ECU and Relay

66CHASSISÐBRAKES
4. Hydraulic Circuit
The hydraulic circuit of the Nippondenso and Bosch systems are the same.
5. Operation
The hydraulic system of the ABS has 4 circuits. Although the hydraulic circuit described below is 1 circuit, it is
applicable to other circuits as well.
During Normal Braking (ABS not activated)
During normal braking, the ABS is not activated
and the ECU does not send control signal. When the
brake pedal is depressed, the fluid pressure in the
master cylinder rises, brake fluid passes from port
A to port B, and then flows to the brake wheel
cylinder. When the brake pedal is released, brake
fluid returns from the brake wheel cylinder to the
master cylinder through port B to port A and the No.
1 Check Valve.

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS ECUOperation
Pressure
Holding ValveOFFPort AOpen
Pressure
Reduction
Valve
OFFPort DClosed
Pump MotorOFFRotating

Hydraulic Circuit

67 CHASSISÐBRAKES
During Normal Braking (ABS not activated)
1) Pressure Reduction Mode
When the wheel is about to lock, the control signal
from the ECU causes port A to close, port D to open,
thus engaging the pressure reduction mode.
At this time, the brake fluid flows from the wheel
cylinder, through ports C and D, to the reservoir,
reducing the wheel cylinder pressure. At the same
time, the brake fluid is pumped and returned to the
master cylinder.

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS ECUOperation
Pressure
Holding ValveONPort AClosed
Pressure
Reduction
Valve
ONPort DOpen
Pump MotorONRotating
2) Pressure Holding Mode
After the fluid pressure in the wheel cylinder is
reduced or increased to the required pressure, a
control signal fromt he ECU causes ports A and D
to close. As a result, the system engages in the
pressure holding mode to maintain the fluid
pressure in the wheel cylinder.

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS ECUOperation
Pressure
Holding ValveONPort AClosed
Pressure
Reduction
Valve
OFFPort DClosed
Pump MotorONRotating

Hydraulic Circuit

Hydraulic Circuit

68CHASSISÐBRAKES
3) Pressure Increase Mode
When the fluid pressure in the wheel cylinder needs
to be increased in order to apply more braking force,
a control signal from the ECU causes port A to open,
port D to close, thus engaging in the pressure
increase mode.
Accordingly, the circuit will be in the same state as
in normal braking, in chich the brake fluid is sent
from the master cylinder to the wheel cylinder to
increase the fluid pressure in the wheel cylinder.
The fluid pressure increase rate is controlled by
repetition of the pressure increase and pressure
holding mode.

Condition of Each Valve and Pump Motor
Part Name
Signal from
ABS ECUOperation
Pressure
Holding ValveOFFPort AOpen
Pressure
Reduction
Valve
OFFPort DClosed
Pump MotorONRotating

Hydraulic Circuit

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.

73 CHASSISÐBRAKES
6. Construction and Operation of Components
TRAC OFF Switch and Indicator Light
1) TRAC OFF Switch
When pressing, this switch turns the TRAC system to be inoperative. Pressing it again changes it to be operative.
When turning the ignition switch from ªOFFº to ªONº, TRAC system always becomes operative.
2) TRAC OFF Indicator Light
This light comes on when the TRAC system is set inoperative by the TRAC OFF switch, and informs the driver
accordingly. And blinks to alert the driver when a malfunction has occurred in the engine and TRAC system.
3) Slip Indicator Light
When the TRAC system is operative, the light blinks and informs the driver accordingly.
ABS & TRAC Actuator
1) Construction
The ABS & TRAC actuator consists of 12 two±position solenoid valves, 1 motor, 2 pumps 2 reservoirs and 2 pressure
regulator valves.
The 12 two±position solenoid valves consists of 2 master cut solenoid valves, 2 reservoirs cut solenoid valves, 4
pressure holding valves, and 4pressure reduction valves.
Pressure regulator valve is assembled into the master cut solenoid valve.
The basic construction and operation of the pump, reservoir, pressure holding valve, and pressure reduction valve
are shared with ABS.
a. Master Cut Solenoid Valve
When the TRAC system is active, a signal from the ABS & TRAC ECU causes the master cut solenoid valve to turn
ON in order to shut off the circuit between the master cylinder and the front brake wheel cylinder.