Toyota Sienna Service Manual: System description
1. BRIEF DESCRIPTION
- The CAN (Controller Area Network) is a serial data
communication system for real time application. It is
a vehicle multiplex communication system which
has a high communication speed (500 kbps) and
the ability to detect malfunctions.
- By pairing the CANH and CANL bus lines, the CAN
performs communication based on differential
voltages.
- Many ECUs (sensors) installed on the vehicle
operate by sharing information and communicating
with each other.
- The CAN has 2 resistors of 120 Ω which are
necessary to communicate with the main wire.
2. DEFINITION OF TERMS
- Main wire
The main wire is a wire harness between the 2
termination circuits on the bus (communication line).
This is the main bus in the CAN communication
system.
- Branch wire
- The branch wire is a wire harness which
diverges from the main wire to an ECU or
sensor.
- Terminating resistors
- Two resistors of 120 Ω resistance are installed in
parallel across the ends of the CAN main bus
wires. They are called terminating resistors.
These resistors allow the changes of the voltage
differential between the CAN bus wires to be
accurately judged. To allow for proper function of
CAN communication, it is necessary to have
both terminating resistors installed. Since the
two resistors are installed in parallel, a
measurement of resistance between the two
CAN bus wires should produce a reading of
approximately 60 Ω.
3. ECUS OR SENSORS WHICH COMMUNICATE
THROUGH CAN COMMUNICATION SYSTEM
- ECM
- Network gateway ECU
- Skid control ECU with actuator*1
- Steering angle sensor*1
- Yaw rate sensor*1
- Distance control ECU*2
HINT:
*1: with VSC
*2: with Dynamic laser cruise control
4. DIAGNOSTIC CODE FOR CAN COMMUNICATION
SYSTEM
- DTCs for the CAN communication system are as
follows: U0073, U0100, U0122, U0123, U0124,
U0126 and U1101.
HINT:
If U0235 or U1102 is output alone, the CAN
communication in normal (See page CC-88
forU0235, See page CC-91 for U1102).
5. TROUBLESHOOTING REMARKS
- DTCs for the CAN communication system can be
checked using the intelligent tester via the CAN
VIM. The DLC3 is connected to the CAN
communication system, but no DTCs exist
regarding problems in the DLC3 or the DLC3 branch
wires. If there is trouble in the DLC3 or the DLC3
branch wires, ECUs on the CAN network cannot
output codes to the intelligent tester via the CAN
VIM.
- Trouble in the CAN buses (communication lines)
can be checked by measuring the resistance
between terminals of the DLC3. However, an open
circuit in a branch wire other than the DLC3 branch
wires cannot be checked from the DLC3.
NOTICE:
Do not insert the tester probes directly into the
DLC3. Be sure to use a service wires.
NOTICE:
DTCs for the CAN communication system are as follows:
U0073, U0100, U0122, U0123, U0124, U0126 and U1101.
HINT:
If U0235 or U1102 is output alone, the CAN communication is
normal
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