Toyota Sequoia (2005). Manual - part 523

DIDF6–01

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–1887

2081

MULTIPLEX COMMUNICATION SYSTEM

PRECAUTION

NOTICE:
When disconnecting the battery terminal, initialize the following system after the terminal is recon-
nected.

System Name

See Page

Back Door Power Window Control System

BE–77

DIDF7–01

I28466

DLC 3

Front 
Passenger
Door ECU

Body ECU

A/C ECU

Combination
Meter

Back Door
ECU

Driver Door
ECU

MPX1

MPX2

MPX3

Slide Roof
ECU

Memory
Seat ECU
& Switch

MPX1

MPX2

MPX1

MPX2

MPX1

MPX2

MPX–

MPX+

MPX1

MPX1

SIL

Automatic Light
Control Sensor

Wireless Door
Control Receiver

Airbag Sensor Assy

Diagnostic Bus

BEAN

CLTS

CLTB
CLTE

PRG

GSW

OBD2

PDA

DI–1888

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

2082

SYSTEM DIAGRAM

DIDFN–01

B78765

I28978

Battery

Serial Communication

Switch

ECU

On

On

Off

ECU

Light

Motor

Heater

Solenoid

 Conceptual Drawing 



I28977

Frame

Data

Header

End Message

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DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

DI–1889

2083

SYSTEM DESCRIPTION

Basic of MPX (Multiplex Communication)
1.

General

The SEQUOIA multiplex communication system uses serial communication, which converts multiple pieces
of information into serial communication data. As a result, they can be transmitted through a single commu-
nication wire.

Serial communication data consists of bits and frames. A bit is the basic unit that represents the amount of
information. A bit is represented by a binary value ”0” or ”1”. A frame is a body of data that is transmitted
together. A frame contains a ”header” that indicates the beginning of the data and an ”end message” that
indicates the end of the data.

B78774

I28976

ECU

ECU

ECU

ECU

Daisy
Chain

Open

DI–1890

–

DIAGNOSTICS

MULTIPLEX COMMUNICATION SYSTEM

2084

2.

Network Style

Based on serial communication, various ECUs are connected on a network to exchange various pieces of
information. Such a system is called  a multiplex communication system.



The BEAN (Body Electronics Area Network) uses the ring and bus styles of networks to connect ECUs.
This connection style is called a daisy chain. In the daisy chain, communication can be maintained
even if there is an area that has an open circuit.