Section 455 (Multiplex Communication System - Diagnostics): Pre-Check

WARNING: This page is about a different car, the 2005 Lexus RX 330. However, it is still accessible from the selected car via links, so may be relevant.

MULTIPLEX COMMUNICATION SYSTEM (BEAN) DESCRIPTION
1. The BEAN communication line is used to control the following items:
  - Airbag sensor assy (Airbag ECU)
  - Combination meter assy (Meter ECU)
  - Power window regulator master switch assy A/C amplifier (A/C ECU)
  - Multiplex tilt & telescopic ECU
  - Transponder key ECU ECM
  - Center cluster integration switch assy
  - Network gateway ECU
  - Rain sensor
  - Sliding roof drive gear assy (Sliding roof ECU)
  - Headlamp swivel ECU (AFS ECU)
  - Multiplex network door ECU back (Power back door ECU)
  - Position control ECU & switch assy (Power seat ECU)
  - Windshield wiper relay assy (Wiper ECU)
  - Driver side outer mirror control ECU
  - Passenger side outer mirror control ECU
    If there is a short-circuit (bus-down) in the line, communication to the system that has a short-circuit (bus-down) will be disabled and the DTC concerning the system will be output from the multiplex network body ECU.
  Fig 1: Communication Diagram - Multiplex Communication System (BEAN)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. If DTC indicating ECU communication stop is output, the connectors may be disconnected or the communication buses may be open at 2 points. Only 1 communication bus open will not set DTC.
  
  Fig 2: Communication Diagram - DTC Indicating ECU Communication Stop Is Output
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. If 2 communication buses are open at the positions as shown in the illustration, DTC indicating ECU communication stop between those 2 buses is output.
  
  Fig 3: Communication Diagram - Communication Buses Are Open At Positions
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DIAGNOSIS SYSTEM

Inspect the DLC3.

HINT:

The vehicle's ECM uses ISO 9141-2 for communication.

The terminal arrangement of the DLC3 complies with SAE

J1962 and matches the ISO 9141-2 format.

Fig 4: Identifying DLC3 Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DLC3 CONNECTOR TERMINALS REFERENCE

Terminal No.	Condition	Specified Condition
7 (Bus + line) - 5 (Signal ground)	During communication	Pulse generation
4 (Chassis ground) - Body ground	Constant	Below 1 Ω
5 (Signal ground) - Body ground	Constant	Below 1 Ω
16 (B+) - Body ground	Constant	9 to 14 V

HINT:

If the display shows UNABLE TO CONNECT TO VEHICLE when you have connected the cable of the handheld tester to the DLC3, turned the ignition switch ON and operated the hand-held tester, there is a problem on the vehicle side or tester side.

If communication is normal when the tester is connected to another vehicle, inspect the DLC3 of the original vehicle.
If communication is still impossible when the tester is connected to another vehicle, the problem is probably in the tester itself, so consult the Service Department listed in the tester's instruction manual.

Check the battery voltage.
Battery voltage: 11 to 14 V If voltage is below 11V, recharge the battery before proceeding.

CHECK DTC
1. Connect the hand-held tester to the DLC3.
2. Turn the ignition switch ON.
3. Read DTCs by following the prompts on the tester screen.
  HINT:
  
  Refer to the hand-held tester operator's manual for further details.
CLEAR DTC
1. Connect the hand-held tester to the DLC3.
2. Turn the ignition switch ON.
3. Erase the DTCs following the prompts on the tester screen.
  HINT:
  
  Refer to the hand-held tester operator's manual for further details.