Lexus ES300 (2002 year). Service manual — part 85

BODY ELECTRICAL – ACCESSORIES

BE-38

187BE38

Bit Size comparison

CD

DVD

Second
Layer
First
Layer

182BE49

Detection Portion

Vibration Direction

Turning Axis Center

Coriolis Force

DVD (Digital Versatile Disc)

The DVD, which uses a smaller laser beam diameter than the CD (Compact Disc), is able to record and play
back a greater amount of data because it can handle pits, or signal grooves, at a higher density. The volume
of data that a 12 cm (0.47 in.) diameter DVD can store is equivalent to approximately 7.5 times that of a
CD-ROM, totaling 4.7 gigabytes. The navigation system has adopted a dual-layer DVD, which has two lay-
ers per side to store a large capacity of signal data, totaling 8.5 gigabytes.

Gyro Sensor

The gyro sensor is designed to detect the yaw rate of vertical axis turn of the vehicle and installed in the
Navigation ECU.
The gyro sensor has a piezoelectric ceramic piece inside. This piezoelectric ceramic piece deforms by charg-
ing voltage and generates voltage by deforming with force.
The piezoelectric ceramic piece inside the gyro sensor is vibrated by the driving circuit and when the vehicle
turns (when the detection portion turns to the axis direction), coriolis force is added to the detection portion.
With this force, the detection portion is twisted. The voltage generated by this twisting is signal-processed
inside the gyro sensor and outputted.
Navigation ECU receives this signal and judges the yaw rate of the vehicle.

BODY ELECTRICAL – ACCESSORIES

BE-39

151BE24

GPS Satellites

Difference

Difference

Difference

Difference

Detection the Vehicle Position

The navigation ECU calculates the position based on the principle of a 3-point measurement.
The GPS satellites are equipped with high-precision clocks. Thus, the satellites are able to transmit continu-
ous orbit signals and radio wave transmission time signals.
The navigation ECU also contains a clock, which can understand the radio wave time signals that are re-
ceived from the satellites.
As a result, the length of time that is taken by the radio waves to arrive from the satellites to the antenna
can be determined. Thus, the lengths of time that elapse for the radio waves of the 4 satellites to reach the
antenna are measured. Each of these lengths of time are multiplied by the luminous flux (the rate of trans-
mission of luminous energy: approximately 300,000 km / second), the results of which are the distances
from the satellites to the antenna. Because the positions of the GPS satellites are known by their signals,
the receiving point (vehicle position) can be rendered as the point in which the 4 spheres (of which the cen-
ters are the respective satellites) converge.
However, due to the differences that exist between the clocks of the satellite and the ECU, the 4 spheres do
not converge at a single point. Therefore, the ECU uses another satellite to calculate the point at which the
4 spheres converge at a signal point and corrects its internal clock. As a result, the ECU determines the ve-
hicle position and adjusts its internal clock to the clocks of the satellites.

BODY ELECTRICAL – ACCESSORIES

BE-63

211BE42

Seat Position
Memory
Switch

Memory
Mirror ECU

Memory
Seat ECU

211BE43

Power
Seat
Switches

Seat Position
Memory
Switch

Ignition
Switch

Park / Neutral
Position Switch

Driver Door
Courtesy
Switch

Memory Seat ECU

Pulse Generation Circuit

Memory
Mirror ECU

LH
Outside
Rear View
Mirror

RH
Outside
Rear View
Mirror

Slide

Front
Vertical

Rear
Vertical

Reclining

Driver Seat

MEMORY SYSTEM

1. General

On the ’02 ES300, a memory system for the driver seat is provided as optional equipment.
The memory seat ECU effects control by memorizing two seat positions and outside rear view mirror posi-

tion.

On the ’01 ES300, the seat position was detected by the Hall IC that is installed on the power seat motor.

However, the ’02 ES300 has adopted a new mechanism to detect the seat position, in which the memory
seat ECU converts the driving current pulsations generated by the rotation of the motor into pulse signals.

System Diagram

BODY ELECTRICAL – ACCESSORIES

BE-64

211BE58

Current pulsations
generated by motor

Pulses after
conversion

Pulse Generation
Circuit

Power Seat
Motor

Memory Seat
ECU

Pulses corresponding
to motor speed

Hall IC

Power Seat
Motor

Memory Seat
ECU

’02 ES300

’01 ES300

2. Construction

Seat Position Detection

On the ’01 ES300, the Hall IC that is installed on the power seat motor generated the number of pulses that
corresponded to the speed of the motor. These pulses were then picked up by the memory seat ECU in order
to detect the seat position.
On the ’02 ES300, however, a pulse generation circuit in the memory seat ECU converts the driving current
pulsations that are generated by the rotation of the motor into pulse signals. These signals are then picked
up in order to detect the seat position. As a result, the construction of the system has been simplified.